ENCE 


UNIVERSITY  OF  CALIFORNIA 
AT   LOS  ANGELES 


THE  GIFT  OF 

MAY  TREAT  MORRISON 

IN  MEMORY  OF 

ALEXANDER  F  MORRISON 


/'• 


EARLY  CHAPTERS   IN  SCIENCE 


EARLY    CHAPTERS 
IN    SCIENCE 


A  FIRST  BOOK  OF  KNOWLEDGE 
OF   NATURAL  HISTORY,  BOTANY,  PHYSIOLOGY 
PHYSICS  AND  CHEMISTRY 
FOR  YJOUNG:  PEOPLE'*.  "" 


BY 

MRS.   W.   AWDRY 

EDITED  BY 

W.  F.  BARRETT 

PROFESSOR   OF   EXPERIMENTAL   PHYSICS    IN   THE 
ROYAL   COLLEGE   OF   SCIENCE    FOR    IRELAND 


WITH  NUMEROUS  ILLUSTRATIONS 


NEW  YORK 
E.   P.   BUTTON   &   CO. 

LONDON 

JOHN   MURRAY,  ALBEMARLE  STREET 
1899 


LONDON  : 

PRINTED    BY    WILLIAM    CLOWES   AND   SONS,    LIMITED, 
STAMFORD   STREET    AND   CHARING   CROSS. 


PREFACE. 


WHEN,  in  the  autumn  of  1897,  the  Author  of  this  little 
book  left  England  to  accompany  her  husband,  Bishop 
Awdry,  to  his  diocese  in  Japan,  she  placed  the  manu- 
script in  my  hands,  and  asked  me,  as  an  old  friend, 
whether  I  would  write  a  brief  introduction  and  find  a 
publisher,  if,  in  my  judgment,  I  thought  the  book  likely 
to  be  useful.  This  I  gladly  consented  to  do,  as  there 
appeared  to  be  a  distinct  want  for  an  elementary  book 
on  science  of  this  kind.  I  therefore  submitted  the 
manuscript  to  Mr.  Murray,  and  he  at  once  undertook 
its  publication.  And  here  I  may,  perhaps,  be  allowed 
to  express  both  my  own  and  the  Author's  great  indebted- 
ness to  Mr.  A.  H.  Hallam  Murray,  who  has  kindly 
devoted  much  time  to  the  superintendence  of  the  illus- 
trations and  other  details. 

The  object  of  the  book  is  to  provide  young  people, 
especially  the  junior  classes  in  schools,  with  an  intro- 
duction to  the  two  great  divisions  of  science — Biological 
and  Experimental ;  to  the  World  of  Life  and  the  World 


439414 


VI  PREFACE. 

of  Experiment.  The  first  part  of  the  book  teaches 
the  boy  or  girl  to  observe,  the  second  part  to  question, 
Nature.  Whilst  the  young  reader  is  throughout  led  to 
feel  he  is  still  only  on  the  threshold  of  scientific  know- 
ledge, the  aim  has  been  to  make  the  work  accurate  as 
far  as  it  goes;  so  that  the  reader,  whilst  he  will  have 
much  more  to  learn,  need  not  fear  he  will  have 
much  to  unlearn.  For  this  purpose  I  have  gratefully 
to  acknowledge  the  invaluable  help  rendered  by  several 
scientific  friends  who  undertook  the  revision  of  different 
parts  of  this  book  : — Mr.  G.  H.  Carpenter,  B.Sc.,  Assistant 
Naturalist  in  the  Science  and  Art  Museum,  Dublin, 
kindly  revised  the  part  on  Zoology :  my  colleague,  Pro- 
fessor T.  Johnson,  D.Sc.,  F.L.S.,  Professor  of  Botany  in 
the  Royal  College  of  Science,  Dublin,  the  section  on 
Botany :  Professor  J.  A.  Scott,  M.A.,  M.D.,  F.R.C.S.I., 
Professor  of  Physiology  in  the  Royal  College  of  Surgeons, 
Dublin,  the  chapter  on  Physiology :  Mr.  H.  Ramage, 
F.I.C.,  F.C.S.,  Assistant  Chemist  at  the  Royal  College 
of  Science,  Dublin,  the  chapter  on  Chemistry.  I  have 
revised,  and  in  some  parts  rewritten,  the  section  on 
Physics,  and  have  especially  to  thank  my  learned  friend 
the  Rev.  Maxwell  H.  Close,  M.A.,  for  also  reading 
the  proof  sheets  of  this  section,  and  for  many  valuable 
suggestions.  Nearly  all  the  illustrations  were  drawn 
specially  for  the  work,  and,  as  regards  Part  I.,  direct 
from  nature,  either  from  the  animals  themselves  in  the 
Zoological  Gardens,  or  from  the  collections  in  the 


PREFACE.  Vll 

Natural  History  Museum,  at  South  Kensington.  For  the 
attractiveness  thus  given  to  its  pages,  thanks  are  due 
to  Miss  L.  Stevenson,  Miss  J.  Mothersole,  and  others 
to  whom  were  entrusted  this  part  of  the  work.  Thanks 
are  also  due  to  Mr.  C.  E.  Lawrence  for  the  preparation 
of  the  Index  and  Table  of  Contents,  etc. 

The  wide  success  which  M.  Paul  Bert's  "  First  Year 
of  Scientific  Knowledge "  has  attained  in  France,  en- 
courages me  to  hope  that  a  somewhat  similar,  but  more 
modest  attempt,  may  be  found  of  use  in  England. 
Mrs.  Awdry's  "  Early  Chapters  in  Science,"  whilst  more 
elementary  and  not  covering  so  wide  a  field  as  M.  Paul 
Bert's  volume,  is  written  in  a  more  attractive  style,  and 
avoids  the  kind  of  scientific  "  pemmican  "  which  charac- 
terizes M.  Bert's  volume,  and  which  must  be  to  young 
people  so  indigestible,  and  favourable  to  mere  cram. 
The  object  of  the  present  little  book  will  be  attained 
if  it  awakens  in  its  young  readers  an  intelligent  interest 
in  this  wonderful  world  in  the  midst  of  which  we  live, 
and  a  desire  to  know  more  of  the  procession  of  life 
and  unfolding  of  phenomena  which  it  is  the  business  of 
science  to  arrange  in  an  orderly  sequence. 

W.  F.  BARRETT. 
January,  1899. 


TABLE    OF   CONTENTS. 


PART   I. 
THE   WORLD   OP   LIFE. 

THE  ANIMAL  AND  VEGETABLE  KINGDOMS. 
CHAPTER  I. 

CLASSIFICATION. 

PAGE 

The  first  division — Vertebrate  animals — Hot-blooded — Mam- 
mals—Birds—Cold blooded— Reptiles,  amphibians,  fishes 
— Invertebrate  animals — The  main  divisions — Multitudi- 
nous varieties — A  table  of  the  animal  kingdom  ...  3 


CHAPTER   II. 
MAMMALIA. 

Man — Apes — The  various  kinds  of  monkeys — Bats — Insect 
eaters — Flying  lemur,  a  connecting  link — Beasts  of  prey 
— Land  carnivora — The  cat  family — Hyena — The  dog 
family — Bears — Weasels — Marine  carnivora — The  whale 
family — Sirenia  ...  ...  ...  ...  •••  25 


CONTENTS. 


CHAPTER   III. 
MAM  MALTA — continued. 

PAGE 

Elephants — The  coney  family — Hoofed  animals — The  horse 
family — Tapirs — Rhinoceros — Swine  —  Hippopotamus — 
Ruminants — The  ox  family — Sheep,  goats,  and  antelopes 
— Giraffes— The  deer  family— The  growth  of  antlers- 
Camels — The  hump — Llamas — Rodents  or  gnawing 
creatures — The  squirrel  group — Rats  and  mice  — Porcu- 
pine— Hares  and  rabbits — Edentata — Sloths — Ant-eaters 
— Marsupials  or  pouched  animals — Egg-laying  mammals  52 


CHAPTER   IV. 

BIRDS  (Aves). 

Distinctions  of  this  class — The  egg — Birds  of  prey — Picarian 
or  wood-pecking  birds — The  parrot— Climbing  birds — 
Perching  birds — The  songsters — Game  birds  and  pigeons 
—Waders— Water  birds— Wingless  birds— Nests— Won- 
derful varieties  ...  ...  ...  ...  ...  91 


CHAPTER   V. 

•REPTILES   AND   AMPHIBIANS. 

Characteristics  —  Tortoises — Crocodiles — Lizards — Snakes — 
Poisonous  and  not  poisonous — Amphibia — The  develop- 
ment from  tadpole  to  frog  ...  ...  ...  ...  107 


CHAPTER   VI. 

FISHES. 

Fins — Various  families  of  fish — Sea  and  fresh-water  fish       ...     1 15 


CONTENTS. 


CHAPTER   VII. 

INVERTEBRATE  ANIMALS. 

PAGE 

Great  number  of  minute  creatures — Mollusca — Shell-fish — 
Arthropoda — The  life  history  of  an  insect — The  busy  bee 
— The  fly  group — Centipedes — Crustaceans — Worms — 
Vast  numbers— Echinodermata—Coelenterata— Jelly-fish 
— Sponges — Protozoa — Lowest  forms  of  animal  life — 
From  a  single  cell  to  the  highest  forms  of  life  ...  ...  121 


CHAPTER   VIII. 

PHYSIOLOGY. 

The  human  body — Bones — The  jointed  back-bone — Simi- 
larities of  the  bone-structure  among  the  vertebrata — The 
limbs — Clavicles — Muscle — How  it  contracts — Inside  the 
body — The  diaphragm — The  heart — How  it  does  its  work 
— The  blood — Comparisons — The  stomach — The  digestive 
apparatus — The  brain — Nerves — The  senses — The  ear 
and  the  eye — The  nerve  centres  of  the  invertebrate  ...  137 


CHAPTER   IX. 

PLANTS. 

Different  forms  of  roots — Trailers  and  creepers — Leaves — 
Flowers — The  parts  of  a  flower — Examination  of  various 
flowers  and  blossoms — Many  different  shapes  of  flowers — 
The  seed  and  its  development — Dicotyledons — Monoco- 
tyledons— Coniferne — Flowerless  plants  ...  ...  167 


CHAPTER   X. 
PLANT  LIFE. 

The  length  of  a  plant's  life — Tissues — How  a  plant  feeds — 

Cells— Effect  of  sunlight  on  plants — Flesh-eating  plants       191 


xii  CONTEXTS. 

PART   II. 
THE   WORLD    OF   EXPERIMENT. 

THE    FORCES   OF   NATURE. 
CHAPTER  XI. 

FORCES  AT   WORK. 

PAGE 

Gravitation — Why  have  unsupported  objects  a  tendency  to 
fall  ?  —  Various  forces  —  Cohesion  —  Heat  —  Chemical 
affinity — Electricity — Friction — Definition  of  force  ...  199 

CHAPTER   XII. 

ENERGY. 

Work  and  the  capacity  for  doing  work — Potential  energy — 
Active  or  kinetic  energy  —  Transference  of  energy — 
Energy,  indestructible  and  yet  ever  changing — A  swing- 
ing weight — Momentum  and  gravitation  ...  ...  207 

CHAPTER   XIII. 

WEIGHT  AND   DENSITY. 

Velocity  of  falling  objects — Effect  of  the  resistance  of  the 
air  —  An  experiment  —  Momentum  —  Transformation  of 
energy — Density  and  volume — Specific  gravity — Why 
iron  ships  float  ...  ...  214 

CHAPTER   XIV. 

PRESSURE   OF   FLUIDS.      THE   BAROMETER. 

Transmission  of  pressure  in  liquids — Pressure  of  gases — Air 
has  weight — The  working  of  a  pump — The  barometer — 
What  it  measures — How  it  is  made...  ...  ...  223 


CONTENTS.  XI 11 


CHAPTER   XV. 

THREE  STATES  OF  MATTER — COHESION. 

PAGE 

From  ice  to  vapour — A  simple  experiment — All  things  exist 
as  solid,  liquid,  or  gas — The  effects  of  heat  and  cold — 
Cohesion — Heat  the  enemy  of  cohesion — Evaporation — 
Solution — Crystallization — Various  crystals  ...  ...  231 


CHAPTER   XVI. 

HEAT. 

I  low  steel  expands — A  thermometer,  and  what  it  measures — 
Freezing  point  and  boiling  point — Centigrade  and  Fahren- 
heit thermometers — Temperature — Specific  heat — Fusion 
— Latent  heat — Density  of  ice  and  water — Force  of  ex- 
pansion— Steam  in  a  kettle — Convection — Conduction — 
Good  and  bad  conductors — Radiation 


CHAPTER   XVII. 
LIGHT. 

Luminous  bodies— Transparency,  translucency,  opacity — Re- 
flected light — Colour — Regular  reflexion— Proof  of  law 
of  reflexion — Simple  experiments — Refraction — Apparent 
place  of  objects  altered  by  refraction — Proportion  of  light 
reflected — Effects  of  refraction — Prisms  and  lenses — The 
speed  at  which  light  travels 


CHAPTER   XVIII. 

SOUND. 

Its  velocity— The  telephone— Connexion  of  sound  and  motion 
— Vibrations— An  air  pump — Musical  sounds — Music 
and  mathematics  ... 


CONTENTS. 


CHAPTER   XIX. 

MAGNETISM. 


Experiments  with  a  magnet — The  north  and  south  poles  of  a 
magnet — Lines  of  magnetic  force — The  mariner's  compass 
— Magnetism  of  the  earth  ...  ...  ...  ...  285 


CHAPTER  XX. 

ELECTRICITY. 

The  nature  of  electricity  unknown — Frictional  electricity — 
Conduction  and  insulation — Doubleness  of  electricity — 
Positive  and  negative  electricity — Electroscopes — Electric 
distribution — Induction — Current  electricity — A  voltaic 
battery — Electro-magnetism  — The  telegraph  —  Electric 
lighting  ...  ...  ...  ...  ...  ...  292 


CHAPTER    XXI. 

CHEMISTRY. 

Analysis  of  water — Decomposition — Hydrogen  and  oxygen — 
Elements  and  compounds— Combination  and  mixture — 
A  table  of  elements— Metals  and  non-metals— Nitrogen 
—Carbon— Phosphorus  and  Sulphur— Oxidation— Acids 
— Combustion — A  flame — Respiration— Carbonic  acid 
gas — Hard  and  soft  waters — Diffusion  of  gases — Con- 


clusion 


3°9 


INDEX  339 


LIST   OF    ILLUSTRATIONS. 


PART    I. 


ZOOLOGY. 

Skeleton  of  Snake  .  . 
Frog  
Worm 

PAGE 
5 

7 

12 
13 
13 
13 

13 
13 
13 

H 
14 
14 
»4 

19 
23 
27 
28 
29 
30 
32 
33 
33 
34 
« 

Hedgehog  
Flying  Lemur  (Colugo)     . 
Cat's  Teeth      .... 
Skeleton  of  Lion    .     .      . 
Lion 

PAGE 
36 

37 
38 
39 
40 
43 
45 
46 

47 
47 
48 
49 
50 
53 
55 
56 
58 
60 
61 

63 
64 

65 

66 
68 
70 

72 

Slug 

Snail 

Hyena   
Fox        

Wolf 

Wasp     
Butterfly,     with      Closed 
Wings      
Caterpillar  
Spider    
Centipede   
Shrimp  
Sea-Anemone  .... 
Starfish        ... 

Bear       

Weasel        ... 

Otter      
Seal       
Whale    
Coney    
Tapir     
Rhinoceros       .... 
Hippopotamus 
Indian  Ox,  or  Zebu    . 
Bison     
Mountain  Goat,  or  Ibex  . 
Gazelle  
Gnu       
Antlers  of  Deer  in  succes- 
sive years  
Head  of  Reindeer 
Chevrotain       .... 
Llama    . 

The   Chief   Sub-divisions 
of  Animal  Life  . 
Genealogical  Tree      .      . 
Skeleton  of  Gorilla     .      . 
of  Man     .... 
Chimpanzee     .... 
Entellus  Monkey   . 
Baboon  
Lemur   

Bat,  with  Spread  Wings  . 
Bones  of  the  Wing  of  a  Bat 
Mole  . 

LIST  OF  ILLUSTRATIONS. 


I 

Flying  Squirrel      .      .      . 

AGE 

74 
76 
77 
78 
79 
81 
82 
83 
84 
86 

88 
89 

93 
95 
96 

97 
99 

IOI 

1  02 
103 
104 
105 
108 
109 

IIO 

in 

112 

"3 
"5 
116 
116 
117 
118 
119 
119 

121 

Whelk  
Scallop        
Solen     
Caterpillar        .... 
Pupa     
Butterfly 

PAGE 
123 
123 

"3 
I24 
124 
124 

125 
126 
126 
127 
127 
127 
128 
129 
131 
132 
132 
133 
134 
134 

135 

139 
144 
I48 

I49 
'S3 
154 
»54 
155 

155 

I58 

Rat 

Jerboa  
Porcupine         .... 
Sloth     . 

Great  Ant-bear 
Pangolin     
Armadillo  

Beetle,  with  Spread  Wings 
Bee  .     . 

Ant  . 

Crane  Fly   . 

Opossum,  with  Young  on 
her  Back       .... 
Duck-billed  Platypus  (  Or- 
nithorhyncus}    . 
Sections  of  an  Egg  showing 
development  of  the  Chick 
Condor  
Owl       
Woodpecker    .... 
Bird  of  Paradise    .      .      . 
Flamingoes      .... 
Albatross    

Grasshopper     .... 
Earwig,  Flying 
Scorpion     
Crab      

Sea-Urchin       .... 
Jellyfish 

Sea-Anemone  .... 
Coral 

Sponge       
Living  Foraminifer  (much 
magnified)    .... 

PHYSIOLOGY. 

Skeleton  of  Fowl  .      .      . 
Bones  of  Arm,  with  Biceps 
Muscle    
Human  Thorax  and  Abdo- 
men laid  open    . 
Diagram  of  the  Circulation 
through  the  Heart  . 
Blood  Corpuscles  . 
Heart  of  a  Frog     .      .      . 
Heart  of  a  Fish      .      .     . 
Stomach  of  a  Man 
Compound  Stomach  of  a 

Penguin      
Ostrich        .... 

Tailor-bird's  Nest 
Tortoise 

Crocodile    

Lizard  
Viper     
Head  of  Venomous   Ser- 
pent showing  Fangs 
Tadpole  and  Frog  in  Dif- 
ferent Stages      .      .     . 
Skeleton  of  a  Perch    . 
Salmon       
Shark    
Sunfish  
Skate    

Flatfish       .      . 

Diagram      showing      the 
Human  Brain   and  the 
Spinal  Cord  .... 

Cod       ... 

Octopus      

LIST  OF  ILLUSTRATIONS. 


Section  of  Eyeball  .  . 
Nervous  System  of  Frog  . 
Nervous  System  of  Earth- 


PLANTS. 


PAGE 
163 
I64 

165 


Buttercup  Plant 
Oak  Tree    
Daisy     

167  ; 

168 
169 

Plantain      

170 

Dandelion  
Potato 

171  i 

Turnip  
Lily  of  the  Valley  .      .      . 
Spruce  Fir  

171 

171  1 

172 

Stem  of  Convolvulus  . 
Virginia  Creeper    . 
Tendrils  of  Pea      .      .      . 
Flower  of  Poppy   . 
Plantain      
Cuckoo-flower 
Carrot 

173 
173  i 

174  ] 
176 
176 
176 

176 

Daisy,  with   Two  Florets 
separated      .      . 
Apple  Blossom 
Section  of  Apple  Blossom 

177 
178 
179 

Section  of  Pistil  and  Re- 
ceptacle of  Buttercup   .  1 79 
Primrose  Blossom        .      .  180 
Lily  of  the  Valley  Blossom  18 1 
Blossom  of  Sweet  Pea      .  181 
Ovules  of  Pea  in  Pod  .      .  182 
Germination  of  Bean  .      .  184 
Mustard  Plant,  with  Coty- 
ledons     and       Second 

Leaves 185 

Harebell 186 

Snowdrop 1 86 

Wallflower        ....  187 

Daffodil 187 

Palm  Tree 188 

Germination  of  Spruce  Fir  188 

Cellular  Tissue       ...  193 

Woody  Tissue  .      .      .      .  193 

Vascular  Tissue     .      .      .  193 
Magnified  Tip  of  Rootlet, 

with  Root  Hairs      .      .  194 
Timber  cut  across,  showing 
Rings  and  Crack  during 

Drying 197 

Dodder  on  Heather    .      .  197 
Sundew    Plant,   and    one 

Leaf  closing  over  Fly   .  198 


PART    II. 


PHYSICS. 

Ball  Swinging  to  illustrate 
Alternating  Types  of 
Energy 

Coin  and  Feather  falling 
in  vacuo  

Water  spouting  from  Butt 

Uniform  Level  of  Water 
in  Can  and  Spout  . 


I  )iagram  of  Suction  Pump     227 
Construction   of   a   Baro- 
meter        229 

Water    distilled    from    a 

213   |       Kettle 232 

!  Group  of  Alum  Crystals  .     238 
215       Crystals  of  Alum,  Common 

224  |       Salt,  etc 238 

Experiment       illustrating 

225  Expansion  by  Heat       .     242 


LIST  OF  ILI.VSTKATIOXS. 


Experiment       illustrating 
Analogy  of  Water-level 
and  Temperature    . 
Diagram  of  Reflexion  . 
Experiment  to  show  the 
Law  of  Reflexion    . 
Experiment  to  show  Re- 
fraction   

PAGE 

245 
265 

266 
267 

The  Common  Chord  of  (i 
Magnet  and  Keeper    . 
Knitting-needle      magne- 
tized and  suspended 
Magnetic   Curves,  similar 
Poles  juxtaposed 
Magnetic   Curves,   unlike 
Poles  juxtaposed 

•84 

285 

287 
288 
280 

Pencil  Reflected  in  Mirror 
Apparent     Place    of   Re- 
flected Object    .     .      . 
Apparent   Place   of  Coin 
altered  by  Refraction    . 
Refracted  Image  of  Stick 
in  Water       .... 
Prism    

269 
270 
271 

272 
273 

Magnetic  Needle  .     .      . 
Suspended  Pith  Balls  .     . 
Mode  of  suspending  Rod 
Gold-leaf  Electroscope 
Experiment       illustrating 
Electric  Induction  . 
Simple    form    of  Voltaic 
Battery 

Boy 
290 
294 
295 
297 

300 

7O4 

Convex      and      Concave 
Lenses     •      .                 . 

*  /  -j 
2T\ 

Bar  of  Iron  magnetized  by 

J^T1 
•7OC 

Refraction  of  Light  by  a 
Convex  Lens 
Formation  of  an  Enlarged 
inverted    Image    by    a 
Double  Convex  Lens    . 
A  Toy  Mechanical  Tele- 
phone       
Air  Pump  

*/  o 

274 

274 

277 
28l 

CHEMISTRY. 

Decomposition   of  Water 
by  Electric  Current 
Sulphur       and       Copper 
heated  in  a  Test-tube   . 

J°5 

310 
315 

The    Middle    C    on    the 
Pianoforte    .... 

283 

Preparation   of   Nitrogen 
from  Atmospheric  Air   . 

319 

EARLY  CHAPTERS  IX  SCIEXCE 


PART  I. 

THE   ANIMAL  AND  VEGETABLE 
KINGDOMS. 

CHAPTER    I. 

CLASSIFICATION. 

PROBABLY,  when  any  one  speaks  of  animals  and  animal 
life,  we  all  think  first  of  horses  and  cows,  cats  and  dogs, 
and  other  conspicuous  or  useful  animals,  or  perhaps  of 
lions,  tigers,  and  elephants. 

But  a  little  thought  will  remind  us  of  many  other 
varieties  of  living  creatures,  some  of  them  differing  so 
widely  from  these  that  they  seem  to  have  nothing  in 
common  but  the  fact  of  their  all  being  alive. 

Suppose  we  sit  down  quietly  in  a  shady  country  garden 
in  early  summer,  and  make  a  list  of  the  live  creatures 
that  come  under  our  notice  in  the  course  of  half  an  hour. 

The  first  we  see  make  us  smile,  for  they  are  baby  and 
the  kitten,  having  a  game  of  play ;  and  next  a  flock  of 
sheep  passes  bleating  along  the  road,  while  the  busy  and 
important  sheep-dog  barks  at  the  stragglers.  But  when 
they  are  gone  by  and  all  is  quiet  again,  shyer  creatures 
begin  to  venture  in  sight.  What  is  that  bonny  ball  of 


4  ANIMAL  AND    VEGETABLE   KINGDOMS. 

brown  fur\Wancing\dnf  the' branch  of  the  larch  tree,  and 
nibbling  ;spme,thing  .held  in  .its.  paws  ?  It  is  not  every 
garden'  that  is'  enlivened  ^  by1  "sqmrrels  with  their  pretty 
gambols,  but  I  know  one  that  is  their  constant  and 
welcome  haunt. 

Now  the  whole  air  is  musical  with  the  voices  of  the 
birds;  the  thrush  is  never  tired  of  his  song,  a  cuckoo 
is  proclaiming  himself  from  the  wood,  numberless  small 
birds  are  busily  twittering  and  chattering  over  their  young 
families,  and  here  comes  a  swallow  darting  and  turning 
after  the  flies.  Ah  yes,  the  flies ;  why,  there  are  crowds 
and  crowds  of  them  dancing  in  the  sunny  air,  and  supply- 
ing food  enough  alike  for  the  birds  and  the  spiders.  At 
midday  the  flies  are  but  a  slight  annoyance ;  but  if  we 
linger  in  the  garden  till  evening  we  know  well  that  at 
five  o'clock,  or  thereabouts,  their  places  will  be  taken 
by  swarms  of  midges,  to  the  sorrow  of  any  one  who  is 
sensitive  to  midge  bites ;  and  when  the  swallows  go  to 
bed,  out  will  come  the  bats  pursuing  gnats  and  midges 
with  their  swift  silent  flight. 

If  we  look  attentively  at  the  rough  ground  under  the 
shrubbery  we  shall  see  that  the  fallen  leaves  and  rubbish 
lying  there  are  constantly  in  motion.  What  is  moving 
them  ?  On  examining  a  little  more  closely  we  find 
beetles,  snails,  ants,  and  numberless  other  small  creatures 
at  work  there.  Turn  over  that  log  of  wood,  and  many 
earwigs  hurry  off  in  all  directions  on  important  business, 
while  the  woodlice  are  trying  to  roll  themselves  up  into 
pills,  and  a  toad  which  had  sheltered  there,  crawls 
leisurely  into  a  cooler  and  darker  retreat. 

Our   list   may    grow   much   longer    yet.      There   are 


THE  FIRST  DIVISION.  5 

butterflies  at  play  in  the  sunshine,  green  aphis  on  the  rose 
trees,  bees  buzzing  about  the  flowers,  while  the  ripple  of 
the  stream  at  the  foot  of  the  hill  reminds  us  that  its  cool 
waters  are  full  of  fish.  I  do  not  suppose  we  shall  see  a 
garden  snake  or  a  lizard,  as  these  are  comparatively  rare. 
But  we  want  another  creature  that  has  not  appeared 
yet,  so  let  us  walk  round  where  the  gardener  is  digging 
among  the  vegetables,  and  see  what  he  turns  up.  Ah, 
here  it  is,  a  fine  fat  wriggling  earthworm  !  Lay  it  on  the 
hard  path  where  we  can  have  a  good  look  at  it.  Is  it 
not  like  a  snake?  They  are  both  long,  narrow,  round 
creatures,  without  legs,  which  wriggle  along  upon  the 
ground.  But  is  a  worm  a  snake  ?  No ;  you  shake  your 
heads,  you  know  better  than  that.  Yet  I  am  not  so  sure 
that  you  can  say  what  is  the  great  difference  between 
them— a  difference  so  important  as  to  put  them  on 
opposite  sides  in  the  one  great  division  that  runs  through 
all  the  animal  creation ;  probably  you  have  never  looked 
inside  either  of  them  to  see  how  they  are  made. 


Here  is  a  picture  of  a  snake's  skeleton.     If  the  skin  and 
the  flesh  of  a  snake  were  all  taken  away,  we  should  find 


6          ANIMAL  AND    VEGETABLE  KINGDOMS. 

these  bones  left — a  head,  and  a  long  flexible  backbone 
with  numeixms  ribs  coming  out  of  it,  bent  round  somewhat 
into  the  shape  of  the  creature — a  framework  of  a  snake. 

Well,  what  about  the  worm  ?  Ah,  we  are  beginning 
to  see  the  difference.  A  worm  has  no  bones  at  all ;  if 
the  body  of  a  worm  is  cut  open,  its  structures  are  found 
to  be  all  quite  soft ;  there  is  no  hard,  bony,  framework. 

However  alike  they  may  outwardly  appear,  this  is 
indeed  a  main  distinction,  and  by  means  of  it  we  may 
arrange  all  animals  into  two  divisions— animals  that  have 
a  bony  skeleton  on  which  the  body  is  built  up,  and 
animals  that  have  not. 

Take  the  list  of  creatures  in  the  garden,  and  see  how 
they  are  divided  by  this  test.  Now  that  your  attention  is 
drawn  to  it,  no  doubt  you  can  tell  in  a  moment  in  which 
division  most  of  them  are  to  be  placed.  Certainly  baby 
has  bones ;  and  the  sheep,  for  we  have  seen  mutton 
bones ;  and  dogs  and  cats,  for  we  have  known  of  their 
bones  being  broken  in  traps ;  yes,  and  so  have  the 
squirrels,  and,  in  fact,  all  the  four-legged  animals.  What 
about  the  birds?  Every  one  who  has  seen  a  fowl  or 
any  other  bird  on  the  dinner-table  knows  the  look  of  its 
bones,  and  if  birds  are  alike  they  must  all  have  bones. 
Then,  fish-bones  are  familiar  enough  to  everybody,  and 
some  of  us  think  fish  hardly  worth  eating  on  account  of 
them.  Has  the  frog  bones?  Perhaps  you  are  not  so 
certain  about  this;  but  here  is  a  picture  of  a  frog's 
skeleton,  which  puts  the  matter  beyond  a  doubt. 

But  they  all  seem  to  have  bones;  what  is  there  left 
to  go  into  the  other  class  ?  Let  us  look  back  at  our  list, 
and  see  what  else  there  is.  Snails  and  slugs.  Their 


BONY  AND  BONELESS   CREATURES. 


bodies  are  soft  enough.  We  may  examine  them  with- 
out finding  any  trace  of  hard  frame-work;  and  the  flies, 
bees,  and  butter- 
flies, if  trodden  on, 
will  be  crushed 
quite  flat ;  there  is 
nothing  inside 
them  hard  enough 
to  resist  pressure. 
And  the  same  may 
be  said  of  the 
spiders  and  wood- 
lice,  as  well  as  the 
worms.  Most  of 
the  insects,  indeed, 
have  rather  hard 
cases,  but  no 
skeleton  inside. 
These  are  all  little 
creatures;  and 

though  there  are  a  few  large  ones  in  the  sea,  yet  the 
great  majority  of  the  boneless  creatures  are  compara- 
tively small,  for  which,  however,  they  amply  make  up 
by  their  countless  numbers,  both  on  land  and  in  the 
water. 

We  need  go  no  further  than  the  two  pictures  of 
skeletons  already  given,  to  see  that  there  is  a  good  deal 
of  difference  in  the  number  and  shapes  of  bones  in 
different  creatures.  Some  creatures  have  legs,  some  have 
tails,  some  have  both,  and  bones  to  support  them  are 
present  or  absent  accordingly.  Every  animal,  however, 


Skeleton  of  Frog. 


8  ANIMAL  AND    VEGETABLE  KINGDOMS. 

that  has  any  bones  at  all,  always  has  a  backbone, 
formed  of  separate  pieces  or  joints,  more  or  less  easily 
movable  one  upon  another;  and  from  this  the  whole 
great  division  gets  its  scientific  name  of  Vertebrate 
Animals,  or  Vertebrata,  from  the  Latin  word  vertebra, 
a  joint,  which  is  used  of  the  joints  of  the  backbone. 
The  boneless  creatures  are  called  Invertebrate  Animals, 
or  Invertebrate ;  but  we  will  put  these  on  one  side  for  the 
present,  and,  turning  our  attention  to  the  Vertebrate 
Animals,  try  if  we  can  find  some  other  good  test  by 
which  to  divide  them  again  into  two  sets. 

Take  this  frog  in  your  hand,  and  tell  me  what  it  feels 
like.  It  is  not  poisonous,  there  is  nothing  to  be  afraid 
of;  yet  it  is  an  unpleasant,  cold,  slimy  creature,  and  no 
one  is  very  willing  to  handle  it.  But  we  do  not  mind 
touching  other  creatures.  Only  see  how  pussy  is  caressed. 
Ah,  pussy  is  not  cold  and  slimy ;  she  is  quite  soft  and 
warm.  Warm  and  cold !  Well,  take  this  for  the  next 
division,  and  see  which  of  the  Vertebrate  creatures  are 
warm  and  which  are  cold.  We  can  feel  the  dogs  and 
the  sheep,  the  cows  and  the  horses,  and  find  that  they 
are  all  warm.  The  wild  birds  will  not  let  us  touch  them, 
but  in  the  poultry-yard,  perhaps,  we  can  get  hold  of  a 
downy  young  chick  newly  hatched,  and  feel  what  a  hot 
little  thing  it  is.  And  when  the  hen  chaffinch  flies  off 
her  nest  we  can  feel  her  eggs,  which  are  quite  warm  from 
the  heat  of  her  body.  To  be  sure,  birds  generally  keep 
their  eggs  warm  by  sitting  on  them,  so  they  must  be  all 
warm  themselves. 

Speaking  of  birds'  eggs  reminds  us  that  we  have  yet 
one  more  division  to  make  among  the  creatures  with 


MAMMALS,   BIRDS,    REPTILES.  9 

warm  blood :  we  must  separate  those  that  lay  eggs  from 
those  that  do  not.  The  cows,  horses,  sheep,  and  many 
other  animials  are  born  alive,  and  nourished  for  some 
time  by  their  mothers'  milk.  Creatures  born  and  nourished 
in  this  way  are  called  Mammals,  or  Mammalia,  and  all 
the  warm-blooded  animals  known  are  either  Mammals, 
or  else  belong  to  the  Birds,  which  are,  as  we  know,  first 
produced  as  eggs,  out  of  which  the  young  birds  are 
hatched  under  the  influence  of  heat. 

Now,  let  us  in  the  same  sort  of  way  try  and  divide  into 
two  or  three  classes  the  cold  and  slippery  Vertebrata, 
among  which,  besides  frogs  and  toads,  we  must  reckon 
the  snakes  and  lizards,  and  all  the  fish.  These  creatures 
are  all  produced  from  eggs,  which  are  generally  deposited 
before  hatching,  although  in  a  few  instances  the  eggs  are 
retained  in  the  body  of  the  mother  until  they  are  hatched, 
so  that  the  young  are  born  alive.  We  must  therefore 
look  for  some  other  dividing  line  among  them,  and  a 
very  important  one  is  afforded  by  their  manner  of 
breathing. 

If  we  watch  a  live  fish  in  a  pan  of  water,  we  shall  see 
a  constant  heaving  movement  of  two  openings  set  one  on 
each  side  of  the  head,  an  apparent  opening  and  closing 
of  little  doors.  The  little  doors  are  the  gill-covers,  and 
if  they  were  removed  we  should  see  behind  them  the 
gills,  a  series  of  delicate  membranes  so  transparent  that 
we  can  see  the  blood  through  them,  making  them  look 
quite  red.  The  gills  are  the  breathing  organs  of  fishes  ; 
for  fishes  can  only  breathe  air  contained  in  water,  and  die 
when  the  gills  become  dry.  But  gills,  which  require  to 
be  always  wet,  would  not  at  all  suit  the  snakes  and  other 


10        ANIMAL  AND    VEGETABLE  KINGDOMS. 

creatures  living  on  dry  land,  and  they  breathe  by  lungs, 
like  the  mammals  and  birds.  The  name  for  most  cold- 
blooded Vertebrate  animals  breathing  by  lungs  is  Reptiles, 
while  those  that  breathe  by  gills  belong  to  the  Class  of 
Fish, 

In  which  of  these  classes,  then,  are  we  to  put  the  frogs 
and  toads  ?  Why,  they  can  live  on  land  and  breathe  dry 
air,  so  we  take  it  for  granted  that  as  they  have  lungs  they 
must  be  Reptiles.  Ah,  but  think  of  their  history  !  When 
frogs'  eggs  are  hatched,  frogs  do  not  come  out,  but  tad- 
poles, which  swim  about  in  water  and  breathe  by  gills 
like  fishes ;  then,  as  they  grow  older,  they  gradually 
develop  lungs,  lose  their  gills,  turn  into  frogs,  and  come 
out  of  the  water.  Gills  first  and  lungs  afterwards.  Then 
they  ought  to  belong  to  both  classes.  In  fact,  they  are 
reckoned  a  separate  Class,  which  stands  between  the 
other  two,  and  is  named  Amphibians,  or  Amphibia,  from 
two  Greek  words,  meaning  "  life  in  both  ways." 

Thus  we  have  arranged  all  the  Vertebrate  animals  into 
five  classes. 

I.  Mammals. — Creatures  with  warm  blood,  whose  young 
are  born  alive,*  and  nourished  by  their  mothers'  milk. 

II.  Birds. — Creatures  with  warm  blood,  whose  young 
are  hatched  out  of  eggs. 

III.  Reptiles. — Creatures  with   cold   blood,  breathing 
only  by  lungs. 

IV.  Amphibians. — Creatures  with  cold  blood,  breath- 
ing both  by  gills  and  by  lungs. 

*  Except  the  Australian  duckbill,  and  spiny  anteaters,  which  lay 
eggs  from  which  the  young  are  hatched.  They  form  the  lowest  order 
of  mammals,  showing,  by  their  structure,  affinity  to  the  Reptiles. 


TRUE   CLASSIFICATION.  \\ 

V.  Fishes. — Creatures  with  cold  blood,  breathing  only 
by  gills.* 

It  is  clear  that  we  might  have  taken  quite  different 
tests  to  form  classes  by;  for  instance,  we  might  have 
reckoned  together  all  the  creatures  that  have  four  legs, 
so  putting  frogs  and  lizards  into  the  same  class  as  the 
mammals ;  or  have  made  a  test  of  the  power  of  flying, 
which  would  include  bats  among  the  birds,  while  it  left 
out  ostriches.  But  the  arrangement  given  above  is  that 
agreed  upon  by  all  naturalists,  and  the  proof  of  a  good 
arrangement  is  when  the  members  placed  in  one  class 
have  many  characters  in  common  and  do  not  depend 
upon  one  alone.  So,  if  flying  were  the  only  test  of  a 
bird,  the  ostriches  would  have  to  be  placed  in  some  other 
class;  but  when  we  find  that  they  are  clothed  with 
feathers  as  birds,  and  only  birds,  are  :  that  they  have 
no  teeth,  but  a  horny  beak,  a  character  belonging  to 
birds  alone :  that  they  lay  eggs,  out  of  which  the  young 
are  hatched,  and  moreover,  that  close  examination  of 
their  structure  shows  that  the  wing-bones  are  present 
though  very  small;  then  we  can  have  no  hesitation  in 
classing  them  as  birds,  though  they  do  not  fly.  Bats,  on 
the  contrary,  are  covered  with  hair,  like  most  of  the 
mammals;  they  have  soft  snouts,  and  a  set  of  sharp 
teeth ;  their  young  ones  are  born  alive  and  suckled  by 
the  mother;  so  that,  in  spite  of  their  power  of  flight, 
they  cannot  be  included  with  the  birds  from  whom  they 
differ  in  so  many  important  characters. 

So  again,  if  we  looked  only  at  its  habit  of  swimming 

*  Except  the  mudfishes,  found  in  rivers  in  South  America,  Africa, 
and  Australia,  which  breathe  also  by  lungs. 


12         ANIMAL  AND    VEGETABLE  KINGDOMS. 

and  living  in  water,  we  might  easily  suppose  a  whale  to 
be  a  fish ;  but  when  on  further  examination  we  find  that 
its  blood  is  warm,  that  it  breathes  by  lungs  and  not  by 
gills,  coming  up  to  the  surface  of  the  water  to  take 
breath,  and  moreover  that  the  young  do  not  come  out 
of  eggs,  but  are  born  alive  and  fed  with  milk,  we  are 
convinced  that  its  true  place  is  among  the  mammals, 
in  spite  of  much  that  is  fishlike  in  its  form  and 
habits. 

Besides  the  five  classes  of  animals  mentioned  above, 
the  soft,  jelly-like  Sea-squirts  (Tunicata)  are  now  gene- 
rally classed  with  Vertebrates,  on  account  of  the  corre- 
spondence of  their  development  with  that  of  the  bony 
animals.  The  Lampreys  and  the  Lancelet,  formerly 
grouped  with  the  Fish,  are  now  considered  worthy  to 
rank  as  independent  Classes. 

Now  for  the  Invertebrate  Animals.  We  must  get 
another  worm,  a  slug  and  a  snail,  a  wasp,  a  butterfly,  a 
caterpillar,  a  spider,  and  a  centipede. 


If  we  were  by  the  seaside,  it  would  be  well  also  to  go 
down  to  the  shore  and  search  for  a  sea-anemone  and  a 
starfish,  which  may  often  be  found  thrown  up  on  the 


INVER  TRBRA  TE  CREA  TURES. 


beach  after  stormy  weather ;  hut  if  these  are  not  to  be 
had  we  must  be  content  with  their  pictures.     A  shrimp, 


Butterfly  (with  closed  wings\ 


Caterpillar. 


Spider. 


too,  is  wanted  in  our  collection,  and  by  the  help  of  the 
fishmonger  we  can  very  likely  get  this  anywhere. 

First  put  the  worm  and  slug  side  by  side  and  notice 


'4 


ANIMAL  AND    VEGETABLE  KINGDOMS. 


the  difference  in  the  way  their  bodies  are  made.     The 
worm   seems    to    be    made   in   a   number   of   different 


Centipede. 


Shrimp. 


Starfish. 


pieces  or  rings  set  one  behind  another  all  down  the  body 
from  the  head  to  the  tail,  while  the  slug  shows  no  such 
divisions.  Which  of  our  other  animals  are  made  in  the 


MOLLUSC  A.  15 

worm  fashion,  of  pieces  or  segments  joined  one  behind 
another  ?  We  pick  out  the  caterpillar,  the  centipede,  and 
the  shrimp  at  once,  but  then  comes  a  doubt.  Well, 
never  mind  whether  the  segments  are  alike  or  not,  pro- 
vided they  are  behind  each  other.  Upon  this  we  add 
the  wasp,  butterfly,  and  spider  to  the  set. 

The  snail's  body  is  not  in  segments ;  it  is  more  like 
that  of  the  slug,  only  it  carries  on  its  back  a  snug  house, 
into  which  it  can  withdraw  on  the  approach  of  danger. 
Place  it  with  the  slug.  Notice  that  both  snail  and  slug 
walk  upon  a  long,  flat,  muscular  "  foot." 

Now  there  are  the  starfish  and  sea-anemone  left.  The 
starfish  does  indeed  seem  to  be  made  of  different  pieces, 
but,  instead  of  being  set  behind  one  another,  they  are 
arranged  all  round  a  centre  in  which  is  the  creature's 
mouth  ;  and  the  anemone,  though  less  divided  up,  is 
of  the  same  general  pattern.  These  two,  therefore,  must 
be  placed  together,  apart  from  the  other  sets. 

Here  we  have  a  few  main  distinctions  among  the 
Invertebrate  creatures. 

The  first  group,  called  Molhtsks,  or  Mollusca,  to  which 
the  slug  and  snail  belong,  have  soft  bodies  enveloped 
in  a  muscular  skin  or  mantle,  and  most  of  them  have 
also  a  shelly  covering,  sometimes  made  like  the  snail's 
in  one  piece,  sometimes  like  the  oyster's  in  two.  The 
"  foot"  is  nearly  always  present  in  some  form. 

The  animals  whose  bodies  show  segments  one  behind 
another  may  be  divided  into  two  groups,  according  to 
whether  they  have  legs  or  not.  Those  that  walk  about 
upon  jointed  legs  have  been  called  Arf/iropoda,  from 
two  Greek  words  meaning  "jointed  legs;"  while  those 


1 6        ANIMAL  AND    VEGETABLE  KINGDOMS. 

that  have  no  legs  belong  to  the  group  of  Worms. 
Among  the  Worms,  too,  are  included  a  number  of 
animals  whose  bodies  are  not  divided  into  segments; 
flat-worms  and  thread-worms,  for  instance.  These  are 
separated  from  Mollusks  by  having  no  foot  or  mantle, 
though  some  of  them  live  in  shells  (Lamp-shells). 

Two  more  groups  are  formed  of  the  creatures  the  parts 
of  whose  bodies  are  arranged  in  stars  or  circles  round 
their  own  mouths.  Those  that  have  prickly  or  spiny 
skins,  like  the  starfishes  and  sea-urchins,  are  called 
Echinodermata  (thorny  skins),  and  the  smooth-skinned 
sea-anemones  and  jellyfish  are  known  as  Zoophytes  (plant 
animals).  Many  Zoophytes,  however,  build  up  a  hard 
framework  to  protect  themselves,  like  the  tiny  coral 
animals;  colonies  of  these,  by  their  united  labours,  are 
able  to  form  vast  living  reefs  and  islands.  The  best 
distinction  between  the  echinoderms  and  the  zoophytes 
will  be  seen  if  we  look  inside  the  animals. 

In  the  starfish,  as  in  all  Vertebrates,  Mollusks,  and 
Arthropods,  we  shall  find  a  distinct  body- cavity  between 
the  inside  of  the  body-wall  and  the  outside  of  the  food- 
canal  (stomach,  &c.).  But  the  sea-anemone  is  merely  a 
hollow  bag  with  the  inside  lining  thrown  into  folds ;  this 
hollow  is  the  creature's  stomach,  and  there  is  no  body- 
cavity  around  it.  Hence  the  sea-anemone  and  its  allies 
are  now  called  Cceknterata  ("  hollow-stomachs  ")  by  most 
naturalists.  In  this  group  we  can  also  include  the 
Sponges,  whose  insides  may  be  like  a  simple  bag,  or  may 
become  branched  into  a  puzzling  set  of  canals.  But 
many  naturalists  nowadays  prefer  to  reckon  the  sponges 
as  a  group  by  themselves. 


SIMPLEST  FORMS  OF  LIFE.  I? 

There  is  yet  another  group,  of  which  it  is  not  easy 
to  show  you  a  specimen.  Its  members  are  creatures 
consisting  of  single  cells,  which  are  simple  living  bodies, 
generally  so  small  that  they  cannot  be  seen  except  with 
the  help  of  a  microscope.  One  of  the  simplest  is  the  little 
creature  called  an  Amoeba,  which  lives  in  ponds.  These 
are  the  simplest  forms  of  animal  life,  and  are  called 
Protozoa.  In  all  the  other  groups  of  animals  we  have 
considered  the  body  is  built  up  of  a  great  number  of  cells. 

All  of  these  groups  are  too  large  and  general  to  be 
considered  as  "Classes"  in  the  same  sense  as  the  five 
Classes  of  the  Vertebrate  animals.  Each  of  them  is  to 
be  compared  with  the  whole  group  of  Vertebrates,  and 
each  can  be  divided,  like  the  Vertebrates,  into  several 
Classes;  the  Arthropoda,  for  instance,  include  at  least 
four,  and  more  likely  six  or  seven,  Classes.  But,  in  truth, 
naturalists  are  not  yet  thoroughly  agreed  as  to  the  proper 
classification  of  these  myriads  of  little  creatures,  and  we 
find  different  arrangements  in  the  books  of  different 
writers.  This  list  will,  however,  be  a  sufficient  guide  in 
the  very  short  account  that  can  here  be  given  of  the 
Invertebrate  animals. 

I.  Mollusks. — Soft    creatures,    showing    no    rings   or 
divisions  along  their  bodies,  generally  provided  with  a 
"mantle"  and  a  "foot,"  and  often  living  in  shells,  such 
as  shellfish,  cuttlefish,  slugs. 

II.  Arthropoda. — Creatures  with  bodies   arranged   in 
successive   rings   or   segments,    and   with  jointed    legs, 
such  as  insects,  centipedes,  spiders,  lobsters. 

III.  Worms. — Creatures  with  bodies  arranged  in  suc- 
cessive rings,  without   legs ;   also  creatures  without  the 

C 


1 8        ANIMAL  AND    VEGETABLE  KINGDOMS. 

ringed    arrangement    of    the    body   and    also    without 
"  mantle  "  or  "  foot."  * 

IV.  Echinodcrmata. — Creatures  with  prickly  skins,  the 
parts   of  whose   bodies  are   arranged   round   a   central 
mouth,  such  as  starfishes  and  sea-urchins. 

V.  Cotlenterata. — Creatures   with    smooth   skins,   and 
without  body-cavities,  usually  with  tentacles  or  soft  arms 
arranged  round  a  central  mouth,  such  as  jellyfish  and 
sea-anemones. 

VI.  Protozoa. — Creatures  consisting  of  simple  cells. 

In  the  diagram  given  on  the  next  page  the  chief  sub- 
divisions of  animal  life  are  shown  in  a  way  that  can  be 
easily  understood  with  a  little  care. 

All  living  creatures  on  the  earth,  from  the  great  whales 
and  elephants  to  the  tiny  beings  that  can  only  be  seen 
with  a  microscope,  are  included  under  one  or  another 
of  the  divisions  given  above ;  and  we  will  now  go  on 
to  learn  something  about  the  Orders  and  Families  into 
which  the  principal  Classes  are  divided.  For  though 
it  would  be  an  endless  task  to  give  even  a  very  slight 
account  of  animals  were  each  to  be  spoken  of  separately, 
yet  by  the  help  of  this  classification  we  may  hope,  even 
in  a  short  space,  to  gain  so  much  knowledge  of  the 
leading  groups  as  to  be  able  to  refer  to  their  proper 
places  most  of  the  animals  we  meet  with,  and  to  make 
it  easier  to  remember  anything  we  may  learn  about  them 
in  future.  Here  is  a  table  which  sets  forth  how  all  the 

*  Worms,  in  fact,  form  a  very  diverse  group,  whose  members 
have  hardly  any  characters  in  common,  so  that  many  naturalists  do 
not  regard  them  as  one,  but  as  several  sub-kingdoms. 


I   1 


SS 

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tfi  - 

sis 


-15  S 

W    S  y 


-I 

S 

I 
I 


20        ANIMAL   AND    VEGETABLE  KINGDOMS. 

living  creatures  known  upon  the  earth  may  be  classified. 
The  names  in  italics  are  those  used  by  all  naturalists, 
whatever  language  they  may  speak. 

TABLE   OF   THE   ANIMAL   KINGDOM, 
i.  VERTEBRATE  ANIMALS. 


Class.                            Order. 

Chief  Groups. 

I.  Mammals            i.   Man*  (Biinana}. 

ii.  Apes,  etc.  (Quaiiru- 

Monkeys  and  lemurs. 

mana) 

iii.  Bats  (Chiropterd). 

iv.  Insect    eaters    (In- 

Shrews,  moles,  hedge- 

sectivord) 

hogs. 

v.   Beasts  of  prey  (  Car- 

Land.—  Cat      group, 

nivord] 

Dog    group,    Bear 

group. 

Water.  —Walrus,  sea- 

lions,  seals. 

vi.  Whales  (Cetacea) 

Including  dolphins. 

vii.  Manatee  (Sirtuiia). 

viii.  Elephants          (fro- 

boscided). 

ix.  Cony  (Hyracoided). 

x.    Hoofed  animals  (Un- 

Horse    group,    tapir, 

gulatd) 

rhinoceros,    swine, 

peccary,  hippopota- 

mus,  oxen,  sheep, 

goats,      antelopes, 

giraffes,  deer,  chev- 

rotains,         camels, 

llamas. 

xi.  Rodents  (Rodentid) 

Squirrels,  rats,  porcu- 

pines,    hares     and 

rabbits. 

*  The  usual  practice  among  zoologists  is  to  class  Man  with  Apes, 
Monkeys,  and  Lemurs  in  one  order  (Primates),  For  if  the  bodily 
structure  of  Man  alone  is  considered,  he  is  found  to  differ  less  from 
the  higher  apes  than  these  do  from  the  lemurs,  or  even  from  the 
lower  monkeys. 


TABLE   OF  THE  ANIMAL    KINGDOM. 


21 


If.   Birds 


III.  Reptiles 


IV.  Amphibians 
V.  Fishes 


Order.  Chief  Groups. 

xii.  "Toothless" animals  Sloths,         anteaters, 

(Edentata]  armadillos, 

xiii.  Marsupials      (Afar-  Kangaroos,         opos- 

stipialia)  sums,  etc. 

xiv.  Egg-lay  ing  mammals  Duckbill,   spiny  ant- 

(Monotremata).  eaters. 

i.   Birds  of  prey  (Acct-    Falcon  group,  owls. 

pitres) 

ii.  Woodpeckers,     etc.     Climbing  birds,  par- 
(Picarite)  rots,    etc.      Wide- 

gaping  birds,  king- 
fishers, etc. 

iii.  Perching  birds  (Pas-     Crow   group,    thrush 
seres)  group,  finch  group, 

starling  group,  lyre 
bird  group. 

iv.   Pigeons  (Columba) 
v.  Game    birds    (Gal-     Fowl,   turkey,   phea- 

lina)  sant,  partridge. 

vi.  Waders  (Gralfa)  Plovers,  cranes,  rails, 

storks,  snipes. 

vii.  Water-birds       (An-     Ducks,     geese,     and 
seres).  swans,    gulls    and 

petrels,   auks    and 
penguins. 

viii.  Wingless  birds     Ostrich,   emu,  casso- 

(Sirnthiones)  wary. 

i.  Tortoises  (Chelonid), 
ii.  Crocodiles     (Croco- 

dilia). 

iii.  Lizards  (Saitria). 
iv.  Snakes  (Ophidia). 


(Amphibia} 

The  orders  of  fishes 
are  too  difficult  to 
be  given  in  a  small 
book  like  this. 


Frogs,  toads,  newts. 


22        ANIMAL  AND    VEGETABLE  KINGDOMS. 


2.  INVERTEBRATE  ANIMALS. 

Sub-Kingdom.  Principal  Classes.  Chief  Groups. 

1.  Mollusks         Cuttle  fish  (Cephalopoda). 
(Mollusca) 

Univalve     shells     (Gas- 
teropoda). 

Bivalve    shells   (Lamelli 
branckiala). 

II.  Creatures        Insects  (Insecta). 

with  jointed     Centipedes     and     milli- 
legs       (Ar-         pedes  (Myriopoda). 
thropoda)         Spiders,  etc.  (Arachnida). 
Crabs  and  lobsters,  etc. 
( Crustacea) . 

III.  Worms 

( Vermcs). 

IV.  Prickly  Starfishes,      sea  -  ur- 

skinned  chins. 

creatures 

(Echino- 

dermata) 

V.  Zoophytes,  etc.  Jelly    fish,    sea  -  ane- 

(Ccelenlerata)  mones,  coral,    and 

sponges. 

VI.  Simplest 

forms  of 
life  (Pro- 
tozoa) 

We  may  arrange  all  these  Classes,  from  the  lowest  and 
simplest  forms  of  life  to  the  highest  and  most  complex, 
in  a  sort  of  genealogical  tree,  "  with  branches  springing 
from  different  levels,  each  branch  again  bearing  twigs, 
some  of  which  rise  higher  than  the  base  of  the  branch 


A    GENEALOGICAL    TREE.  23 

above."  At  present  our  knowledge  is  very  imperfect, 
but  if  we  could  make  a  perfect  scheme  of  this  sort,  it 
would  give  not  only  an  image  of  the  wonderful  unity 


24        ANIMAL  AND    VEGETABLE  KINGDOMS. 

of  the  whole  animal  kingdom,  but  would  also  express 
the  way  in  which  naturalists  believe  the  different  forms 
of  animal  life  are  related  to  one  another.  Here  is 
such  a  genealogical  tree  taken  from  Mr.  J.  A.  Thomson's 
delightful  book  called  "  The  Study  of  Animal  Life."  * 

It  must,  however,  be  borne  in  mind  that  this  picture 
is  only  an  imaginary  sketch,  meant  to  be  nothing  more 
than  a  pleasing  symbol,  with  many  limitations  and 
imperfections.  It  would  be  foolish  to  suppose  any 
naturalist  could  assert  that  the  various  forms  of  animal 
life  arose  from  one  another  exactly  in  the  way  shown 
in  the  picture.  It  will  also  be  understood  that  this 
genealogical  tree  is  not  meant  to  express  anything 
beyond  the  relationship  of  bodily  structure  in  the  animal 
kingdom. 

*  The  small  twigs  from  the  main  trunk  represent  the  way  in 
which  different  classes  of  -worms  may  be  supposed  to  be  little  off- 
shoots at  different  levels. 


CHAPTER   II. 

MAMMALIA. 

Man. — Among  the  Mammalian  creatures  the  first  Order 
is  that  of  human  beings ;  but  though  this  must  be  duly 
noticed,  it  is  not  our  object  to  study  them  here.  It  is 
evident  that  in  our  bodily  frames  we  closely  resemble 
many  other  of  the  animal  inhabitants  of  the  world,  and 
some  account  of  this  resemblance  will  be  given  later ; 
but  even  the  lowest  races  of  men  are  immeasurably 
removed  by  their  mental  and  spiritual  capabilities  from 
the  lower  animals. 

Apes  (Qnadriimana). — We  can  easily  recognize  that 
next  to  man  comes  the  order  of  animals  most  nearly 
resembling  him,  that  of  the  Apes  and  Monkeys.  The 
distinctive  mark  of  the  Order  is  in  the  formation  of  the 
hind  paws,  which  always  have  five  toes,  one  of  them 
being  placed  opposite  to  the  rest  like  our  thumbs,  so 
making  a  true  hand,  able  to  grasp  firmly.  Most  of  the 
apes  and  monkeys  have  also  true  hands  on  their  fore- 
paws,  but  in  some  instances  the  thumb  is  very  small,  or 
altogether  absent.  Their  skin  is  covered  with  hair, 
except  on  the  face  and  the  palms  of  the  hands. 

Monkeys  are  found  both  in  the  Old  and  New  Worlds, 
but  only  in  warm  climates.  When  brought  to  our 


26        ANIMAL   AND    VEGETABLE  KINGDOMS. 

country  they  suffer  much  from  cold,  and  are  very  liable 
to  consumptive  disease. 

There  is  always  something  specially  interesting  to  us 
in  these  "poor  relations"  of  man,  as  they  have  been 
called ;  and  no  doubt  the  feeling  that  they  are  soulless 
caricatures  of  ourselves  causes  a  sort  of  fascination  in 
watching  them,  whether  it  is  combined  with  horror  at 
the  fierce  and  hideous  great  apes,  or  with  amusement 
at  the  grotesque  impishness  of  the  smaller  monkeys. 
The  likeness  to  man  is  not  only  in  the  outward  form, 
but  shows  itself  in  the  way  in  which  many  of  them  will 
weep  with  sorrow  or  distress,  chuckle,  and  even  smile, 
with  amusement,  redden  with  rage,  or  grow  pale  with 
fear ;  and  in  noticing  these  things  we  begin  to  have  an 
uncomfortable  sort  of  feeling  that  there  is  no  very  great 
difference  between  us.  But  if  we  imagine  a  monkey 
reading  this  book,  or  studying  and  classifying  other 
creatures,  we  immediately  see  the  absurdity  of  the 
comparison. 

The  largest  of  the  apes  is  the  great  African  Gorilla, 
which  is  between  five  and  six  feet  in  height  when  full 
grown,  and  is  enormously  strong  in  the  arms  and 
shoulders.  The  gorilla,  like  all  the  other  apes,  is  with- 
out a  tail,  and  when  standing  up  has  a  horrible  likeness 
to  a  very  heavily-built  and  awkward  man,  with  dispro- 
portionately long  arms  and  hideous  face.  It  cannot, 
however,  stand  upright  without  clinging  to  some  support 
with  its  arms,  and  the  knees  are  always  somewhat  bent, 
so  that  it  does  not  really  walk  like  a  man.  Its  strength 
and  ferocity  are  such  that  a  full-grown  male  gorilla  has 
never  been  captured  alive,  though  the  females  and  the 


MAN  AND    THE  ATE.  2J 

young  have  been   taken.     The  gorilla  lives  in  forests; 
sometimes  it  climbs  into  the  branches  of  the  trees,  and 


28        ANIMAL   AND    VEGETABLE   KINGDOMS. 

when  a  band  of  negroes  passes  below  it  has  been  said  to 
reach  down  one  powerful  hind  paw,  and,  seizing  a  man 


APES  OF   VARIOUS  A'LVDS.  29 

by  the  throat,  to  strangle  him  in  its  grasp.  As  it  does 
not  eat  the  man,  this  would  appear  to  be  done — if  the 
story  be  true — from  simple  spite  and  malice. 

The  Chimpanzee,  another  African  ape,  is  more  gentle 
than  the  gorilla.  Chimpanzees  habitually  live  in  trees, 
where  they  make  nests  among  the  branches. 


The  rest  of  the  apes  are  Asiatic,  and  consist  of  the 
Orang-outangs  in  Borneo  and  Sumatra — large  creatures 
covered  with  reddish  hair,  living  entirely  among  trees, 
whose  branches  they  weave  together  into  platforms  to 
sit  upon  ;  and  of  the  Gibbons,  which  belong  to  Sumatra 
and  Malacca,  and  are  not  quite  such  unpleasant-looking 


30        ANIMAL  AND    VEGETABLE  KINGDOMS. 


objects  as  the  other  apes.  The  Gibbons  do  not  exceed 
three  feet  in  height,  and  their  bodies  are  slender  and 
light,  with  small  heads  and  very  flexible  necks,  and  extra- 
ordinarily long  arms;  some  of  them  being  able  to  put 
their  whole  hands  flat  on  the  ground  without  stooping. 
They  are  all  very  agile  in  their  movements,  springing 
from  tree  to  tree  almost  as  if  they  were  flying.  Their 


Entellus  Monkey. 

disposition  is  shy  and  quiet,  and  they  are   capable  of 
being  tamed  and  trained  in  captivity. 

Most  of  the  members  of  the  Order  that  have  tails  are 
called  monkeys,  and  many  different  kinds  of  them  are 
found  in  all  the  warmer  parts  of  Asia,  Africa,  and  America  ; 
but  the  only  monkey  inhabitant  of  Europe  lives  on  the 
rock  of  Gibraltar,  and  is  really  a  North  African  species 
that  has  crossed  the  Straits.  It  is  known  as  the  Barbarv 


BABOONS  AND    THEIR    WAYS.  3! 

ape ;  but  it  is  not  a  true  ape,  for,  though  its  tail  is  reduced 
to  a  mere  knob  or  projection,  yet  a  tail  it  has.  The 
monkeys  have  not  the  disproportionately  long  arms  of 
the  apes,  and  they  generally  go  on  all  fours. 

None  of  the  family  is  better  known  than  the  Entellus, 
the  monkey  that  haunts  the  villages  of  Northern  India, 
and,  being  protected  by  the  religion  of  the  people,  makes 
itself  quite  at  home  there.  It  varies  from  three  to  four 
feet  in  length,  without  reckoning  the  tail,  which  is  often 
longer  than  the  body,  and  it  is  covered  with  greyish 
fur,  growing  darker  with  age.  Troops  of  these  creatures 
live  in  the  banyan  groves,  and  make  themselves  a  great 
nuisance  by  their  cool  familiarity  and  ingenious  thefts,  not 
only  among  the  crops  and  fruits,  but  also  in  the  shops  and 
markets ;  yet  it  appears  that  even  they  are  surpassed  in 
impudence,  grimaces,  and  mischief  by  the  innumerable 
smaller  monkeys  of  the  African  forests,  who  live  a  merry 
life  chasing  each  other  through  the  branches,  chattering, 
screaming,  playing  practical  jokes,  and,  when  they  get 
a  chance,  pulling  out  the  tail-feathers  of  unfortunate 
parrots  who  come  within  reach  of  their  mischievous 
fingers. 

The  Baboons  of  Africa  have  not  the  half-human  look 
of  other  monkeys,  but  their  heads  are  shaped  more  like 
that  of  a  dog ;  a  fact  to  which  they  owe  their  generic  name 
of  Cynocephalus.  They  hunt  together  in  large  troops, 
keeping  strict  discipline  among  themselves,  and  setting 
sentries  to  watch  against  the  approach  of  enemies.  The 
young  are  playful  and  impertinent ;  but  they  get  soundly 
cuffed  by  the  grave  elders  of  the  tribe  if  they  misbehave, 
or  make  a  noise  when  it  is  important  that  they  should  be 


32        ANIMAL   AND    VEGETABLE  KINGDOMS. 

quiet.  They  are  large,  strong  animals,  living  among 
rocks,  and  making  raids  on  cultivated  grounds,  where 
they  commit  great  depredations. 

The   monkeys   of  America   are  entirely  distinct,  and 
there  are  no  families  of  the  tribe  common  to  the  Old 


and  New  World.  The  expressive  names  Howlers,  Spider 
monkeys,  Squirrel  monkeys,  indicate  some  of  their 
characteristics. 

There  is  a  tribe  of  small  animals  living  in  Madagascar 
and  the  neighbouring  islands,  sometimes  called  half-apes, 
but  properly  Lemurs.  They  have  little  monkey  hands, 
and  are  therefore  included  in  the  same  Order,  but  in 
appearance  are  more  like  foxes  or  cats,  being  rather 
pretty  creatures,  with  very  soft  fur,  and  long,  soft,  round 
tails.  They  are  nocturnal  in  their  habits,  sleeping  through 


33 

the  day,  but  collecting  together  at  night  in  large  com- 
panies, and  displaying  great  activity. 


Bats  (Chiroptera). — The   next  Order  is  that  of  the 
Bats,  which  are  distinguished  from  all  other  Mamir.als 


Bat,  with  spread  wings. 

by   their  wings  and  power  of  flight.     Their  bodies  are 

D 


34        ANIMAL   AND    VEGETABLE  KINGDOMS. 

not  unlike  that  of  a  mouse,  but  their  forepaws  have 
enormously  long  fingers,  supporting  the  folds  of  large 
membranes,  which  connect  the  body,  limbs,  and  tail,  and 
form  real  wings.  Bats  are  found  in  all  parts  of  the 
world,  and  vary  in  size,  from  the 
great  Kalong,  or  Flying  Fox  of 
India,  the  spread  of  whose  wings 
measures  four  feet  across,  to  little 
creatures  a  couple  of  inches  in 
length.  Many  of  the  large  foreign 
bats  are  fruit  eaters ;  but  our 
English  bats  feed  entirely  on  in- 
sects.  People  are  often  afraid  of 
bats  ;  but  though  their  swift  silent 
flight,  and  their  appearance  only  at  night,  certainly  give 
a  feeling  that  there  is  a  strange  sort  of  mystery  about 
them,  yet  there  is  nothing  to  be  afraid  of,  and,  indeed, 
if  allowed  to  come  freely  into  our  rooms  in  warm 
weather,  they  often  do  good  service  by  destroying  gnats 
and  other  annoying  insects.  In  the  daytime  they  hook 
themselves  up  in  some  quiet  dark  corner,  and  wrapped 
up  in  their  folded  leathery  wings  are  hardly  to  be 
recognized  except  by  a  practised  eye. 

Insect  Eaters  (Insectivora). — From  the  Bats  we  pass 
to  another  Order  of  creatures,  who  help  to  keep  down 
our  insect  pests.  This  Order  has  not  such  clear  dis- 
tinguishing marks  as  the  two  already  spoken  of;  but  the 
creatures  which  compose  it  cannot  be  included  in  any 
other.  The  rats  and  mice  seem  very  near  them  in  some 
respects,  but  are  clearly  separated  by  their  possession  of 
the  curious  teeth  which  are  the  special  mark  of  their 


INSECT  EATERS.  35 

own  Order;  while  the  smaller  kinds  of  beasts  of  prey 
(Carnivora)  differ  in  their  bones  and  teeth. 

So  the  Insect  Eaters  stand  by  themselves,  consisting, 
in  England,  of  the  Mole,  Shrew,  and  Hedgehog,  and 
they  have  relations  in  all  parts  of  the  world  except  South 
America  and  Australia.  The  Mole  lives,  works,  and 
hunts  underground,  constructing  a  wonderful  dwelling, 
with  tunnels  leading  into  it  in  all  directions,  so  that  it 
is  sure  of  a  way  of  escape  at  the  approach  of  an  enemy. 
Worms  and  grubs  are  its  food,  and  though,  living  in  the 
dark,  its  eyes  are  small  and  little  used,  yet  it  is  wonder- 


Mole. 

fully  keen  in  hearing  and  smell,  by  which  it  detects  and 
follows  its  prey. 

In  our  country  walks  we  are  all  familiar  with  the 
occasional  sight  of  dead  shrews  lying  about,  though  the 
cause  of  their  death  is  unknown.  Possibly  their  strong 
flavour  prevents  their  being  eaten  by  the  creatures  that 
kill  them.  They  are  not  unlike  mice  in  appearance,  but 
the  true  mouse  belongs  to  quite  another  Order  of 
animals.  The  smallest  known  Mammal  in  the  world 
is  a  tiny  Italian  Shrew,  only  an  inch  and  a  half  long  in 
the  body,  and  with  a  tail  of  another  inch. 

The  back  of  the  Hedgehog  is  covered  with  prickly 


36        ANIMAL   AND    VEGETABLE  KINGDOMS. 

spines,  and  it  has  the  power  of  rolling  itself  up  at  the 
approach  of  danger,  so  as  to  present  nothing  but  a  ball 
of  spines.  It  wanders  at  night  in  search  of  its  food, 
trotting  at  a  pretty  rapid  pace,  and  is  not  over  particular 
as  to  what  it  takes.  I  have  seen  it  eating  a  shrew,  and 
it  cannot  be  acquitted  of  the  crime  of  feeding  at  times 
on  young  rabbits,  poultry,  etc.  How  a  hedgehog  walks 
up  steep  staircases  is  best  known  to  itself;  but  when 


Hedgehog. 

kept  in  houses  to  eat  the  cockroaches,  it  may  often  be 
found  in  the  most  distant  and  apparently  inaccessible 
parts  of  the  building. 

We  might  well  be  surprised  at  finding  creatures  so 
apparently  unlike  as  Monkeys,  Bats,  and  the  Insect 
Eaters  placed  next  to  each  other  as  the  three  first 
Orders  of  Mammals;  but  this  is  partly  explained  by 
the  existence  of  a  very  curious  animal  in  Malacca  and 
the  neighbouring  islands,  which  seems  to  partake  of  the 
nature  of  all  three.  It  has  been  known  as  the  Flying 
Lemur,  and  used  to  be  generally  described  as  one  of 
the  Lemurs  ;  but  naturalists  now  consider  that  its  true 
place  is  among  the  Insectirora.  Its  limbs  and  tail  are 


BEASTS   OF  PREY. 


37 


connected  by  a  large  membrane,  which  spreads  out  and 
supports  it  while  leaping  from  tree  to  tree,  as  if  it  were 
really  flying ;  but  it  has  not  true  wings,  and  cannot  fly 


Flying  Lemur  (Colugd). 

upwards'.  It  moves  at  night,  and  by  day  sleeps  hanging 
by  its  hind  feet  from  the  branch  of  a  tree,  like  a  bat. 

Beasts  of  Prey  (Carnivore?). — Now  comes  the  vast 
order  of  beasts  of  prey ;  divided  into  the  Land  Carnivora, 
or  eaters  of  flesh,  and  the  Marine  Carnivora,  eaters  of 
fish. 

All  the  Land  Carnivora  are  armed  with  sharp  claws 
and  teeth.  Of  front  teeth,  or  incisors,  they  have  six  in 
the  upper  jaw  and  six  in  the  lower.  These  are  suc- 
ceeded by  a  large  strong  pointed  tooth  on  each  side, 
corresponding  to  our  eye-teeth,  and  properly  called 
canines,  which  are  the  chief  instruments  by  which  the 
creature  holds  its  prey.  The  back  teeth  are  different  in 


4:39414 


38        ANIMAL  AND    VEGETABLE  KINGDOMS. 

the  different  families.  The  six  pair  of  incisor  teeth  are 
very  characteristic  of  the  order,  for  the  only  other  animals 
which  have  them  are  the  horse  family,  tapirs,  and  some 
swine,  all  of  which  are  easily  distinguished  from  the 
Carnivora  by  having  hoofs  and  not  claws ;  and  also  a 
few  species  of  the  Insectivora,  which  vary  a  good  deal 
in  the  number  of  their  front  teeth. 

Among  the  Land  Carnivora  are  three  main  groups  : 
the  Cat  group,  including  the  families  of  the  cats,  the 
civets,  and  the  hyenas ;  the  Dog  group,  which  has  but 
a  single  family ;  and  the  Bear  group,  in  which,  besides 
the  bear  family,  are  reckoned  the  racoons,  and  the 
numerous  family  of  the  weasels. 

The  beasts  of  prey  are  powerful,  active,  energetic 
animals,  with  very  acute  sight  and  hearing.  Unlike  the 
quiet  cattle  which  feed  upon  grass,  they  have  to  hunt 
their  prey,  and  depend  for  a  livelihood  upon  what  they 
can  catch  and  kill  for  themselves  and  their  children. 
The  young  are  born  helpless,  and  often  blind,  so  that 
they  depend  on  the  care  of 
their  parents,  who  gradually 
educate  and  train  them  to 
provide  for  themselves. 

CATS. — The  characteristics 
of  the  whole  Cat  family  can 
be  well  seen  in  our  domestic 

Cat's  Teeth.  CatS<        Take      PUSS>'     OI1      >'°Ur 

knee,  and,  if  she  will  let  you 
handle  her,  open  her  mouth  and  look  at  her  teeth.  Her 
front  teeth  are  very  tiny,  but  the  canines  are  large  and 
formidable,  and  you  will  see  that  the  back  teeth  also 


CAT  AND  LION.  39 

have  sharp  points,  not  flattened  crowns  like  our  grinders, 
for  as  cats  can  only  move  their  jaws  up  and  down,  and 
not  at  all  sideways,  they  only  chop  and  tear  their  food, 
and  do  not  grind  it.  Their  tongues  are  rough  all  over 
like  a  file. 

Now,  compare  pussy's   limbs  with  this  picture   of  a 
lion's  skeleton.     If  you  pass  your  hand  up  her  hind  leg 


Skeleton  of  Lion. 

you  will  find  the  knee-joint  almost  hidden  in  the  loose 
folds  of  the  skin  of  the  body,  and  can  then  see  that 
what  looks  like  a  knee  turned  backward,  halfway  down 
her  leg,  is  really  the  heel,  the  beginning  of  a  very  long 
foot.  The  cats  walk  only  on  their  toes,  keeping  this 
heel  lifted  well  above  the  ground,  which  gives  them  a 
tread  as  light  and  springy  as  it  is  powerful.  A  cat 
always  strikes  with  its  feet,  and,  in  the  larger  members 
of  the  family,  there  is  immense  strength  in  the  feet  and 
legs,  for  a  lion  will  kill  an  ox  with  a  blow  of  its  paw,  as 
a  cat  kills  a  mouse. 

The   toes    are    armed   with  sharp    claws,  which    can 
be  put  out  or  retracted  at  will.      This  gives  a  double 


4O        ANIMAL   AND   VEGETABLE  KINGDOMS. 

advantage ;  for  when  the  claws  are  drawn  back  they  are 
protected  from  getting  blunted  against  the  ground,  and, 
at  the  same  time,  the  soft  cushions  upon  which  pussy 
then  treads,  give  the  peculiar,  silent,  and  stealthy  step 
with  which  she  steals  upon  her  prey. 

First  of  the  great  Cats  stand  the  Lions.  They  are 
of  a  yellowish,  tawny  colour,  with  a  tuft  of  hair  at  the 
end  of  the  tail,  and  the  head  and  shoulders  of  the  male 


are  covered  with  a  thick  mane,  which  gives  him  his 
majestic  look.  A  full-grown  lion  measures  about  ten 
feet  from  the  nose  to  the  tip  of  the  tail.  His  strength 
and  swiftness  are  prodigious,  and  his  roar  strikes  terror 
into  the  heart  of  every  animal  within  hearing.  He  is 
not  always  anxious  to  attack.  Dr.  Livingstone  writes, 
"  \Yhen  encountered  in  the  day  time,  the  lion  stands  a 
second  or  two,  gazing,  then  turns  slowly  round,  and 
walks  as  slowly  away  for  a  dozen  paces,  looking  over 


LIVINGSTONE'S  EXPERIENCE.  41 

his  shoulder;  then  begins  to  trot,  and  when  he  thinks 
himself  out  of  sight,  bounds  off  like  a  greyhound."  He 
had,  however,  another  story  to  tell  one  day  when  he 
had  attacked  a  lion,  and  shot  at  him,  but  missed  his 
aim. 

"  He  came  with  a  tremendous  roar,  and  Ferns " 
(Livingstone's  horse)  "  whipped  round  like  a  top,  and 
away  at  full  speed.  My  horse  is  a  fast  one,  and  has  run 
down  the  Gemsbok,  one  of  the  fleetest  antelopes;  but 
the  way  the  lion  ran  him  in  was  terrific.  On  came  the 
lion,  two  strides  to  my  one.  I  never  saw  anything  like 
it,  and  never  want  to  do  so  again.  When  he  was  within 
three  strides  of  me,  I  gave  a  violent  jerk  on  the  near 
rein,  and  a  savage  dig  at  the  same  time  with  the  off 
heel,  armed  with  a  desperate  rowel,  just  in  the  nick  of 
time,  as  the  old  mannikin  bounded  by  me,  grazing  my 
right  shoulder  with  his,  and  all  but  unhorsing  me." 

Livingstone  then  jumped  off  his  horse  and  shot  the 
lion. 

Lions  are  found  in  all  parts  of  Africa,  and  in  the 
south-west  corner  of  Asia;  but  the  king  of  the  Asiatic 
wild  beasts  is  the  royal  Tiger. 

The  Tiger  is  of  enormous  size,  sometimes  reaching 
twelve  feet  in  total  length,  extremely  lithe,  graceful  and 
active  in  movement,  and  beautiful  in  colour,  with  black 
stripes  or  spots  upon  a  yellow  ground.  He  is  a  fearful 
enemy  to  cattle,  and  a  tiger  who  has  once  tasted  human 
flesh,  generally  becomes  a  confirmed  man-eater,  when 
no  life  is  safe  in  his  neighbourhood.  "  One  Tiger,  in 
1887-8-9,  killed,  respectively,  twenty-seven,  thirty-four, 
forty-seven  people."  Tiger-hunting  is  generally  undertaken 


42        ANIMAL  AND   VEGETABLE  KINGDOMS. 

by  large  bodies  of  armed  men,  mostly  mounted  on 
elephants. 

The  beautifully  spotted  Leopard,  or  Panther,  occurs 
both  in  Africa  and  in  Asia.  It  is  smaller  than  the  Lion 
or  Tiger,  but  has  an  advantage  over  them  in  being  able 
to  climb  trees. 

In  America  the  places  of  the  lion  and  tiger  are  taken 
by  the  tawny-coloured  Puma,  and  the  Jaguar,  which  is 
spotted  like  a  Leopard ;  and  many  smaller  kinds  of  cats 
are  found  throughout  America,  Asia,  and  Africa,  but 
Europe  possesses  only  the  Wild  Cat,  which,  though 
nearly  extinct  in  Great  Britain,  is  still  found  in  many 
parts  of  the  Continent,  and  several  varieties  of  Lynxes. 

CIVETS. — Next  to  the  true  Cats  comes  the  Family 
of  Civets,  of  which  we  hear  comparatively  little,  as  none 
of  them  belong  to  this  country.  They  vary  considerably 
in  size ;  the  largest  of  them  being  about  fifty  inches  in 
total  length,  the  smallest  not  above  twenty.  In  general 
appearance  they  are  not  unlike  cats,  but  have  longer 
and  more  pointed  noses.  They  walk  on  their  toes, 
but  keep  the  heel  much  nearer  the  ground  than  cats, 
and  their  claws  can  only  be  partially  drawn  back,  not 
entirely  concealed.  Their  home  is  chiefly  in  Africa 
and  Asia,  but  one  species,  the  Genette,  lives  in  Southern 
Europe. 

HYENAS. — The  Hyena  may  be  considered  to  stand 
half  way  between  the  Cats  and  the  Dogs.  It  is  not 
unlike  a  hideous,  degraded-looking  dog,  with  a  long, 
blunt  nose  and  bushy  tail.  It  has  immensely  strong 
teeth  and  jaws,  which  can  crack  even  large  bones ;  but 
it  is  a  cowardly  beast,  and  rarely  kills  food  for  itself, 


THE  DOG  FAMILY. 


43 


preferring  to  follow  the  great  beasts  of  prey,  and  eat  what 
they  leave,  or  haunting  burial-grounds,  where  it  prowls 
at  night  in  search  of  the  dead  bodies,  uttering  cries  like 


a  horrible  discordant  laugh.  It  belongs  to  Africa  and 
parts  of  Asia. 

DOGS. — The  Dog  Family  includes  Dogs,  Wolves, 
Foxes,  and  Jackals.  Their  claws  cannot  be  drawn 
back  at  all ;  and  though  they  walk  on  their  toes,  like 
the  cats,  yet  they  have  not  the  same  power  in  the  paws ; 
and  when  they  attack,  it  is  always  with  their  teeth.  The 
teeth  also  vary  from  those  of  the  cats ;  for  instead  of 
having  all  sharp  cutting  teeth,  the  two  hindermost  teeth 
of  dogs,  above  and  below  on  each  side,  are  grinders, 
with  flattened  crowns. 

There  are  no  animals  that  vary  so  largely  as  domestic 
dogs.  They  are  of  many  colours,  and  of  all  sizes,  from 
the  huge  mastiff  to  the  tiny  toy  dogs  petted  by  ladies. 
We  have  swift  dogs,  like  the  greyhound ;  sporting  dogs, 
like  the  pointer  and  setter ;  fighting  dogs,  like  the  bull- 
dog ;  hunting  dogs,  like  the  foxhound  or  the  terrier ; 


44        ANIMAL  AND    VEGETABLE  KINGDOMS. 

wise,  responsible  dogs,  like  the  collies.  No  doubt  this 
great  variety  is  largely  produced  through  careful  breeding 
and  training  by  men,  but  it  remains  doubtful  whether 
they  really  all  belong  to  the  same  species  or  not.  Dogs 
are  so  constantly  our  companions  that  we  know  more 
of  their  minds,  their  intelligence,  sympathy,  even  of 
their  conscience,  than  is  the  case  with  any  other  animals. 
Who  does  not  know  how  ashamed  of  himself  a  dog 
will  look  when  he  knows  he  has  done  wrong,  how  happy 
he  will  be  when  his  master  is  pleased  with  him,  how 
quickly  he  will  learn  what  he  is  wanted  to  do,  or  how 
quiet  and  gentle  he  will  be  when  he  sees  his  friends  sad 
and  depressed  ? 

In  the  Arctic  regions  the  Eskimos  are  entirely  de- 
pendent on  their  dogs  to  draw  their  sledges  over  the 
ice  and  snow  when  they  move  from  place  to  place,  and 
the  dogs  are  also  employed  in  hunting  Bears  and  Seals, 
but  they  are  only  half-tamed,  and  are  often  very  savage 
and  unmanageable. 

What  is  known  as  the  Cape  hunting  dog,  though  it 
belongs  to  the  same  group,  is  not  one  of  the  true  dogs ; 
but  there  are  real  wild  dogs  in  India,  and  one  in  Australia, 
called  the  Dingo.  Wild  dogs  live  in  burrows,  caves,  or 
hollow  trees.  It  is  a  curious  thing  that  wild  dogs,  and 
even  domestic  dogs  that  have  run  wild,  whine  or  howl 
like  wolves,  but  seldom  or  never  bark ;  it  almost  seems 
as  if  the  barking  of  a  civilized  dog  is  like  an  attempt  to 
imitate  man  in  speaking. 

FOXES. — Foxes  have  more  pointed  snouts,  shorter 
legs,  and  bushier  tails  than  dogs,  and  also  the  pupils  of 
their  eyes  narrow  into  slits  in  bright  light,  like  those 


FOXES— J  A  CKALS—  IVOL  VES. 


45 


of  a  cat.     Their  depredations  among  poultry  and  other 
small  animals  are  well  known. 


JACKALS. — The  Jackal  of  Asia  and  Africa  is  not  very 
unlike  a  yellow  fox.  It  will  follow  larger  beasts  of  prey, 
and  eat  what  they  leave,  or  will  kill  sickly  or  wounded 
animals  for  itself.  Jackals  hunt  by  night  in  packs,  and 
their  wailing  cry  as  they  sweep  by  an  encampment  is 
one  of  the  most  weird  and  melancholy  of  sounds. 

WOLVES.— In  the  Wolf  we  come  to  a  far  more 
formidable  animal.  It  is  about  the  size  of  a  large 
shepherd's  dog,  to  which  it  bears  a  good  deal  of  re- 
semblance. It  will  kill  and  devour  almost  anything. 
Horses  and  oxen  are  pulled  down  by  wolves;  and  in 
winter  when  they  hunt  in  large  packs,  even  a  troop  of 
armed  men  cannot  always  defend  their  lives  from  these 
savage  beasts,  unless  they  can  reach  some  shelter. 
Wolves  used  formerly  to  live  in  the  British  Islands,  and 


46        ANIMAL   AND   VEGETABLE  KINGDOMS. 

it  is  less  than  two  hundred  years  since  the  last  was 
killed  in  Scotland,  while  in  Ireland  they  lingered  also 
into  the  last  century. 


BEARS.— From  the  Dog  group  we  pass  to  the  Bear 
group.  Bears  have  larger  front  teeth  than  cats  or  dogs, 
and  grinders  behind  their  canine  teeth.  They  walk  on 
the  whole  sole  of  the  foot,  which  gives  them  a  slow, 
heavy  tread,  very  different  from  that  of  the  light  creatures 
that  run  on  their  toes.  They  have  long  sharp  claws, 
which  cannot  be  drawn  back;  and  when  attacked  will 
rear  themselves  up  on  their  hind  legs,  and  strike  terrible 
blows  with  their  claws.  Or  they  will  try  to  seize  an 
adversary  in  their  front  paws,  and  squeeze  him  to  death. 
Most  of  the  Bears  are  harmless  enough  towards  men, 
unless  attacked  first  or  pressed  by  hunger.  This, 


THE  BEAR. 


47 


however,  is  not  the  case  with  the  great  Grizzly  Bear  of 
North  America,  nor  with  the  Polar  Bear  of  the  Arctic 
Seas,  both  of  which  are  very  dangerous  creatures,  and 
most  formidable  foes  to  the  hunter.  Bears  feed  on 


mixed  food,  and  most  of  them  appear  to  be  quite  as 
partial  to  vegetable  as  to  animal  food,  and  particularly 
fond  of  sweet  things.  Indeed,  none  of  the  flesh-eaters 
object  to  an  occasional  change  of  diet,  and  even  a  lion 
is  said  to  enjoy  water-melons. 


WEASELS.— Of  Bears  we  happily  see  none  in  England 
except  in  menageries,  but  the  same  cannot  be  said  of 


48 


ANIMAL   AND   VEGETABLE  KINGDOMS. 


the  large  Family  of  the  Weasels.  Long,  slender,  and 
lithe  in  body,  very  short  in  the  limbs,  very  sharp  in  the 
teeth,  and  very  fierce  in  disposition,  are  most  of  its 
members.  Weasels,  Stoats,  Martens,  Polecats,  Ferrets, 
have  a  strong  family  resemblance  to  each  other,  and 
are  all  terrible  enemies  to  poultry  and  other  small 
creatures.  Ferrets  are  frequently  used  in  hunting  rabbits 
and  rats,  as  they  will  go  into  the  animals'  burrows  and 
turn  them  out.  A  larger  cousin  of  theirs  is  the  Badger, 
which  more  nearly  resembles  some  of  the  foreign  mem- 
bers of  the  family.  Lastly  we  come  to  the  Otter,  which 
burrows  in  the  banks  of  rivers,  and  lives  upon  fish, 


being  itself  equally  at  home  in  water  or  on  land.  The 
Sea-Otter  of  the  North  Pacific  varies  from  other  members 
of  the  Order  in  having  only  four  lower  incisors,  and  in 
any  case,  with  its  aquatic  habits  and  its  webbed  feet,  it 
forms  a  natural  link  to  the  next  Family. 

MARINE  CARNIVORA. — The  sea,  as  well  as  the  land, 
has  its  beasts  of  prey,  feeding  upon  the  fish.  These 
are  the  Walrus,  the  Sea  Lions,  and  the  Seals.  The 
limbs  of  all  these  creatures  scarcely  resemble  legs  at 
all,  but  are  modified  into  mere  flappers,  by  which  they 


U'ALKUS  AND  SEALS. 


49 


move   nimbly  and   easily  in   the  water,  but   awkwardly 
on  shore. 

The  Walrus  is  an  enormous  animal,  from  twelve  to 
fifteen  feet  in  length,  and  its  great  tusks,  which  are 
really  the  upper  canine  teeth  immensely  developed,  give 
it  an  extraordinary  and  formidable  appearance,  which 
is  indeed  justified  by  its  fury  in  fight  when  attacked. 
Walruses  congregate  in  vast  herds  along  the  shores  of 


the  Arctic  Seas,  but  upon  any  alarm  they  at  once  make 
for  the  water,  where  they  feel  safe. 

Seals  are  remarkably  intelligent  creatures,  easily  tamed 
and  very  affectionate,  and  in  captivity  they  readily  learn 
to  obey  the  voice  of  their  keepers  and  to  play  many 
tricks.  They  are  much  attracted  by  music,  and  are 
well  known  to  follow  boats  in  which  a  musical  instru- 
ment is  played.  The  valuable  seal-skin  fur  is  not  the 
skin  of  the  true  seals,  but  of  a  species  of  the  sea  lions,  or 
eared  seals,  which  are  often  much  larger  animals.  The 
true  seals  do  not  exceed  five  feet  in  length,  while  some 
of  the  eared  seals  reach  as  much  as  ten  feet. 

All  the  Marine  Carnivora  come  ashore  for  the  birth 

E 


50        ANIMAL  AND    VEGETABLE  KINGDOMS. 

and  nursing  of  their  young,  and  by  this  power  of  coming 
ashore  are  completely  marked  off  from  the  next  Order 
of  the  Mammalia. 

Whales  (Cetacea). — Whales  belong  entirely  to  the 
water,  and  by  ignorant  people  are  often  supposed  to  be 
fish ;  but  though  rather  fish-like  in  form  and  without 
limbs,  yet  they  are  true  Mammals,  warm-blooded  and 
suckling  their  young.  To  the  Whale  family  belong  the 
largest  animals1  known,  some  of  them  exceeding  even  a 


hundred  feet  in  length.  They  have  to  come  to  the 
surface  from  time  to  time  to  breathe,  and  if  unable  to 
do  so  would  be  drowned ;  but  the  intervals  for  which 
they  can  remain  below  vary  in  different  species,  from 
five  minutes  to  an  hour.  Some  of  the  whales  have  teeth, 
but  other  kinds  have  no  teeth,  their  mouths  being 
furnished  with  a  series  of  plates,  of  what  is  commonly 
called  whalebone,  but  more  properly  baleen.  These 
plates  are  solid  where  they  join  the  palate,  but  split 
into  fringes  at  their  loose  edges,  and  serve  as  strainers 
to  keep  in  the  small  shellfish  and  other  creatures  that 


STKANGE  SEA   ANIMALS.  5! 

enter  the  whale's  mouth  with  the  sea  water.  Huge  as 
the  whales  are,  they  have  very  tiny  throat  passages,  not 
more  than  two  inches  across.  Hence  they  live  princi- 
pally upon  the  smaller  kinds  of  crustaceans,  mollusks, 
and  fish. 

The  families  of  Dolphins  and  Porpoises,  however, 
which  belong  to  the  same  Order  as  the  Whales,  have 
not  this  difficulty,  and  make  great  havoc  among  fish. 

Sirenia. — We  will  only  notice  in  passing  another 
small  Order  of  strange  sea  beasts,  to  which  belongs  the 
Manatee,  an  ugly  and  ungainly  animal,  which,  however, 
is  supposed,  from  its  habit  of  lifting  itself  upright  in  the 
water,  and  carrying  its  young  in  its  arm,  to  have  given 
rise  to  the  legends  about  mermaids. 

The  animals  of  this  Order  cannot  be  included  with  the 
Marine  Carnivora,  which  are  all  furnished  with  powerful 
canine  teeth  to  hold  their  prey,  while  the  Sirenia  have  no 
canines  at  all,  and  feed  only  on  seaweeds.  On  the  other 
hand,  they  are  quite  distinct  from  the  Order  of  Whales, 
for  the  Cetacea  have  smooth  bodies,  and  their  nostrils 
or  "  blow-holes,"  as  they  are  called,  set  right  on  the  top 
of  their  heads ;  while  the  Sirenia  have  hairy  bodies,  and 
their  nostrils  on  the  end  of  their  snout.  They  must, 
therefore,  be  set  in  an  Order  by  themselves. 


52        ANIMAL   AND   VEGETABLE  KINGDOMS. 


CHAPTER    III. 

.MAMMALIA — continued. 

WE  must  now  leave  the  sea,  and  return  to  the  land, 
where  we  are  approaching  the  vast  Order  of  the  Hoofed 
Animals;  but  a  word  must  first  be  said  about  two 
Families  which  are  by  some  naturalists  considered  to 
belong  to  it,  while  by  others  they  are  separated  into 
distinct  Orders,  as  not  having  true  hoofs. 

Elephants  (Probosddea). — The  first  of  these  are  the 
Elephants,  the  largest  of  land  animals,  natives  of  Africa 
and  India.  The  Elephant  is  a  great  heavy  creature, 
usually  about  eight  feet  in  height  when  full  grown,  but 
occasionally  reaching  ten  or  eleven  feet,  and  of  a  dark 
grey  colour.  His  great  tusks,  so  much  sought  after  by 
the  ivory  hunters,  are  not,  like  those  of  the  Walrus, 
canine-teeth,  but  are  the  upper  front  teeth,  or  incisors, 
developed  to  a  very  great  length;  and  he  has  also  the 
advantage  of  growing  fresh  grinding  teeth  when  the  old 
ones  are  worn  out.  But  the  most  wonderful  thing  about 
the  Elephant  is  its  trunk,  which  is  really  an  immense 
lengthening  of  its  nose.  The  trunk  can  be  lengthened 
or  contracted,  waved  from  side  to  side,  or  curled  round 
to  carry  food  and  water  to  the  elephant's  mouth,  and  its 
sensitive  tip  can  pick  up  any  small  object  from  the 


RIG  AND  LITTLE  RELATIONS. 


53 


ground.  The  Elephant  has  been  humorously  and  happily 
described  as  "  a  square  animal,  with  a  leg  at  each  corner, 
and  a  tail  at  both  ends  : "  but  few  tails  could  be  so  useful 
as  the  trunk.  Elephants  are  wonderfully  wise  and  teach- 
able beasts,  and  can  be  employed  in  many  ways.  Not 
only  does  their  great  strength  enable  them  to  carry  all 
sorts  of  heavy  burdens,  but  they  will  also  learn  to  pile 
up  stacks  of  logs,  and  even  to  lay  courses  of  masonry 
in  building,  while  it  is  well  known  that  the  keeper  can 
safely  trust  his  child  to  the  care  of  one  of  these  faithful 
attendants. 

Coney  Family  (Hyracoidea). —  The  other  Family 
spoken  of  above  contains  the  little  creature  which  in 
the  Bible  is  called  the  Coney  and  a  few  related  animals 


living  in  Africa.  The  group  seems  very  small  to  have  a 
Family  and  an  Order  to  itself;  but  while  the  skeleton 
shows  resemblances  to  those  of  several  other  animals, 
it  cannot  be  exactly  classed  with  any  of  them.  Coneys 


54        ANIMAL   AND    VEGETABLE  KINGDOMS. 

are  small  thickset  animals  with  short  legs  and  ears.  One 
group  (including  the  animal  mentioned  in  Psalms  and 
Proverbs)  live  in  colonies  among  rocks.  Another,  in- 
habiting South  and  West  Africa,  climb  trees. 

Hoofed  Animals  (Ungulata). — The  Order  of  the 
Hoofed  Animals  must  be  divided  into  groups  somewhat 
in  the  same  way  as  the  Order  of  the  Beasts  of  Prey  ;  and 
the  main  distinction  is  made  by  the  number  of  the  toes. 
The  first  or  odd-toed  group  includes  the  Horses  and 
Asses,  the  Tapir  and  the  Rhinoceros  Families  in  which 
the  middle  toe  is  the  longest ;  in  the  Horse  family  this 
toe  alone  is  developed  and  bears  the  hoof.  All  the 
rest  of  the  hoofed  animals  belong  to  the  immense  group 
of  the  even-toed  or  cloven  hoofs,  which  must  be  further 
subdivided  when  we  come  to  it.  All  the  animals  of  the 
Order  feed  on  vegetables,  except  the  Swine  Family  which 
eat  everything  they  can  get. 

HORSE  FAMILY. — The  Horses  and  Asses,  the  creatures 
with  a  single  hoof  on  each  foot,  are  a  good  deal  like  each 
other,  and  form  only  one  Family,  but  the  Horses  have 
horny  places,  or  warts,  on  the  inner  side  of  each  leg,  and 
tails  all  covered  with  long  hair,  while  the  Asses  have  the 
warts  only  on  the  fore-legs,  and  hair  only  on  the  end  of 
their  tails. 

Their  teeth  are  not  all  close  together,  but  there  is  a 
considerable  space  left  between  the  front  and  back  teeth, 
which  affords  room  for  the  bit  by  which  they  can  be 
controlled  and  guided. 

The  Horse,  like  the  dog,  is  known  to  us  in  a  great 
variety  of  breeds,  but  these  seem  to  be  due  to  careful 
continued  selection,  and  not  to  any  real  difference  of 


THE  HORSE  FAMILY. 


55 


species.  It  is  a  highly  intelligent  and  affectionate  animal, 
and  its  good  memory  for  a  way  once  travelled  has  often 
been  the  saving  of  a  rider  who  has  lost  his  way;  but 
horses  are  very  nervous,  and,  if  frightened  or  distrustful, 
will  often  appear  ill-tempered  or  unmanageable  when  in 
truth  they  chiefly  need  to  be  soothed  or  reassured. 

Our  hardy,  strong  little  Donkeys  are  not  generally  apt 
to  be  very  swift  in  their  movements,  but  most  of  the 
wild  Asses  are  remarkable  for  swiftness  and  wariness. 
Wild  Asses  of  different  species  are  found  both  in  Asia 
and  Africa,  and  Africa  is  also  the  home  of  those  striking 
and  beautiful  creatures,  the  Quagga  and  the  Zebra,  both 
of  whom  belong  to  the  Asses.  The  domestic  Ass  has 
generally  a  single  dark  stripe  across  its  shoulders,  perhaps 
marking  its  relationship  to  the  finely-striped  Zebra. 

TAPIRS. — Tapirs,  which  form  the  second  division  of 


Tapir. 

the  Hoofed  Animals,  are  creatures  about  the  size  of  a 
donkey  with  very  thick   hides,  and   short  trunks;    they 


56        ANIMAL   AND    VEGETABLE  KINGDOMS. 


are  fond  of  water  and  swim  well.  They  are  not  very 
clean  feeders,  but  live  chiefly  on  vegetables,  and  never 
attack  men  unless  hard  pressed  by  hunters.  Their  home 
is  in  Central  and  South  America,  and  in  the  Malayan 
peninsula  and  islands. 

RHINOCEROS. — Perhaps  there  is  hardly  a  more  hideous 
beast  living  than  the  Rhinoceros.  Its  large,  heavy  body, 
sometimes  reaching  12  ft.  in  length,  and  5ft.  loins, 
in  height,  and  thick,  tough  skin,  which  is  much  prized 


Rhinoceros. 

by  African  and  Indian  natives  for  making  shields,  give 
it  somewhat  the  appearance  of  a  huge  pig ;  but,  unlike  a 
pig,  it  carries  either  one  or  two  horns,  not  on  the  top  of 
its  head,  but  set  behind  one  another  along  its  snout.  In 
the  largest  African  Rhinoceros  the  front  horn  varies  in 
height  from  2  ft.  6  ins.  to  4  ft.,  while  the  hinder  one  is 
only  about  12  to  15  inches.  In  spite  of  its  unwieldy 
appearance  the  Rhinoceros  is  a  very  swift  runner,  severely 
trying  the  powers  even  of  good  horses,  and  this  combined 


THE   CLOVEN  FOOT.  57 

with  its  uncertain  temper  and  habit  of  making  attacks 
without  waiting  for  provocation,  make  it  a  very  dangerous 
beast.  Even  the  Elephant  has  a  terror  of  the  Rhinoceros' 
powerful  horn.  It  is  fond  of  wallowing  in  mud,  partly 
perhaps  as  a  protection  against  the  insects  by  which  it  is 
constantly  infested. 

As  the  Families  of  the  Swine  and  the  Hippopotamus 
differ  considerably  from  the  other  two-toed  families,  and 
in  their  heavy  build  and  thick  hides  approach  the 
character  of  the  Rhinoceros  and  Tapir,  and  even  of 
the  Elephant,  it  is  natural  to  take  them  first  for  considera- 
tion among  the  cloven-footed  animals. 

SWINE. — The  Pigs  or  Hogs  have  round  snouts,  cut 
off  abruptly  at  the  end,  and  capable  of  being  moved 
about  a  good  deal,  with  which  they  root  about,  plough- 
ing up  the  ground  as  they  seek  for  food  with  their  very 
keen  scent.  In  their  wild  state  they  are  neither  stupid 
nor  specially  dirty,  and  if  left  to  themselves  they  soon 
run  wild  and  get  back  to  the  fierceness  of  their  natural 
condition.  It  is  not  so  very  long  since  wild  boars 
became  extinct  in  the  British  Isles,  and  they  are  still 
found  in  most  parts  of  Europe,  Southern  Asia,  and 
Northern  Africa.  A  large  wild  boar  is  a  very  powerful 
animal ;  armed  with  strong,  sharp  tusks,  and  being  very 
swift  in  his  movements,  he  will  charge  in  a  most  dangerous 
manner. 

In  India  the  animals,  which  are  fond  of  being  in  thick 
cover,  often  take  up  their  abode  in  the  standing  crops, 
where  they  do  great  damage ;  they  are  hunted  on  horse- 
back with  spears.  They  grow  to  a  great  size,  and  a  male 
has  been  measured  as  much  as  five  feet  nine  inches  in 


58        ANIMAL   AND    VEGETABLE  KINGDOMS. 

length;  the  females  being  smaller  and  having  smaller 
tusks. 

The  hogs  are  replaced  in  America  by  smaller  animals 
of  the  Swine  Family  called  Peccaries,  which  do  not 
exceed  three  feet  in  length.  They  look  harmless  enough, 
but  are  fierce  little  creatures,  running  in  large  troops ; 
and  being  absolutely  fearless,  and  armed  with  small, 
scarcely-seen  tusks,  as  sharp  as  lancets,  are  dangerous 
to  encounter. 

HIPPOPOTAMUS.  —  The  Hippopotamus,  or  River 
Horse,  is  found  only  in  Africa.  This  enormous  creature, 


Hippopotamus. 

though  not  exceeding  about  five  feet  in  height,  is  fre- 
quently eleven  or  twelve  feet  long,  and  it  opens  its  huge 
mouth  with  a  width  of  gape  unapproached  by  any  other 
animal.  It  is  of  a  heavy,  unwieldy-looking  build.  The 
hippopotamus  was  first  brought  to  England  in  1850, 
and  when  full  grown  reached  a  weight  of  four  tons. 

These  animals  live  by  day  almost  entirely  in  the  water, 


RUMINANTS.  59 

where  they  may  be  seen  together  in  large  numbers,  and 
where  they  can  remain  below  for  a  considerable  time 
between  their  breathing  intervals ;  but  at  night  they  often 
come  ashore,  trampling  and  devastating  the  crops  on 
which  they  feed.  They  are  for  the  most  part  quiet  in  dis- 
position when  unprovoked ;  but  a  bull  hippopotamus  in 
a  fury  is  an  enemy  not  to  be  trifled  with,  and  will  easily 
crunch  up  a  boat  in  its  huge  jaws,  while  the  extreme 
thickness  and  toughness  of  its  skin  make  it  very  difficult 
to  kill. 

RUMINANTS. — All  the  other  families  of  the  cloven 
hoofed  animals,  after  the  Pigs  and  Hippopotamus,  are 
characterized  by  a  curious  habit.  Any  one  who  has 
watched  a  Cow  knows  that  after  feeding  she  will  lie 
down  in  a  quiet  spot  and  enjoy  the  food  over  again. 
From  the  peculiar  structure  of  the  stomach  she  is  able 
to  bring  the  food  again  into  her  mouth,  where  it  is 
leisurely  chewed,  and  prepared  for  digesting.  This  action 
is  called  "chewing  the  cud,"  or  ruminating,  and  the 
animals  that  perform  it  are  called  Ruminants. 

The  Ruminants  include  all  cattle,  sheep,  and  goats, 
all  antelopes  and  deer,  and  the  camels  and  llamas. 
Many  of  them  have  horns,  which  are  always  set  side 
by  side  on  the  top  of  the  head,  not  along  the  nose  like 
those  of  the  Rhinoceros.  But  there  is  an  important 
distinction  between  their  horns.  The  cattle,  sheep, 
goats,  and  antelopes  have  hollow  horns,  covering  a  hard 
bony  core,  and  they  remain  through  life,  gradually  grow- 
ing larger ;  but  the  horns  or  antlers  of  the  deer  family 
are  solid,  not  hollow,  and  they  fall  off  and  are  renewed 
every  year. 


60        ANIMAL    AND    VEGETABLE   KINGDOMS. 

OXEN. — No  creature  that  lives  is  more  valuable  and 
useful  to  man  than  the  common  ox.  In  this  country 
we  value  them  chiefly,  while  living,  for  the  sake  of  the 
milk  of  the  cows ;  but  elsewhere  their  strength  is  con- 
stantly used  for  labour,  both  in  ploughing  and  in  drawing 
waggons.  Indeed  in  South  Africa  the  principal  means 
of  travelling  is  in  waggons  drawn  by  teams  of  oxen,  which 
are  less  liable  than  horses  to  the  attacks  of  the  terrible 


Indian  Ox  or  Zebu. 

tsetse  fly  of  that  country.  Then  their  flesh  is  one  of  our 
most  valuable  foods,  and  almost  every  part  of  the  body 
can  be  turned  to  useful  account. 

Cows  are  so  familiar  to  us  that  we  can  closely  observe 
their  ways,  and  it  is  very  curious  to  see  the  order  which 
they  maintain  among  themselves.  The  leading  cow  of 
the  herd  is  supreme  in  dignity;  none  of  the  younger 
animals  will  presume  to  enter  or  leave  the  pasture  before 


THE   OX  FA  MI  I.  Y. 


6l 


her,  and  so  tenacious  is  she  of  her  position  that  it  is  said 
that  when  a  leading  cow  in  Switzerland  was  deprived  of 
the  deep-toned  bell  hanging  round  her  neck  which  gave 
the  signal  to  the  rest,  she  refused  her  food  and  pined 
away,  and  though  the  bell  was  restored,  it  was  too  late  to 
save  her  life. 

In  the  Ox  Family  must  be  reckoned  several  kinds  of 
Asiatic  oxen,  including  the  large   Indian  cattle  with   a 


hump  on  the  back,  the  Yak,  or  long-haired  ox  of  Tibet, 
the  Bisons,  and  Buffaloes.  These  two  last  names  are 
often  mixed  and  applied  to  the  same  animals ;  but 
properly  speaking,  the  Bisons  include  only  the  Aurochs, 
a  nearly  extinct  animal  of  the  forests  of  South-eastern 
Europe,  and  the  North  American  Bisons.  These  last 
have  thick  shaggy  manes  and  beards,  and  are  large 
animals,  the  males  being  about  six  feet  high  at  the 


62        ANIMAL   AND    VEGETABLE   KINGDOMS. 

shoulder.  They  move  about  in  herds,  which  used 
formerly  to  be  often  vast  in  numbers ;  but  they  are 
now  much  reduced  by  hunters,  who  valued  them  for  their 
skins  and  their  excellent  beef. 

Buffaloes  of  different  kinds  are  found  in  South  Europe, 
in  Africa,  and  in  India,  and  are  among  the  largest  of 
the  Ox  tribe,  with  very  large  horns.  Herds  of  tame 
buffaloes  are  kept  like  oxen;  but  wild  ones  are  often 
dangerous,  and  have  a  special  enmity  against  tigers, 
which  they  attack  and  kill.  All  the  buffaloes  are  very 
fond  of  lying  in  mud  and  water,  sometimes  showing 
only  their  noses  and  eyes  above  the  surface,  and  to  this 
position  they  retire  to  chew  the  cud. 

With  the  little  Musk  Ox  of  the  extreme  north  of 
America  we  seem  to  be  passing  from  the  oxen  to  the 
sheep,  as  its  appearance  is  not  very  unlike  that  of  a  ram 
covered  with  long  hair,  which  hangs  nearly  to  the  ground, 
concealing  its  limbs.  The  name  is  derived  from  its 
strong  musky  odour. 

SHEEP. — -The  Sheep  Family  rival  the  oxen  in  their 
usefulness  to  man,  and  have  been  so  long  domesticated 
that  it  is  impossible  to  say  from  what  country  our  breeds 
of  tame  sheep  first  came.  We  read  in  the  very  beginning 
of  history  that  Abel  was  a  keeper  of  sheep,  and  wher- 
ever men  have  migrated  they  have  taken  with  them  this 
docile  animal,  valuable  equally  for  its  flesh  and  its  wool. 
The  breeds  vary  greatly,  especially  in  the  presence 
or  absence  of  horns,  in  one  or  both  sexes,  and  also 
in  activity  and  spirit,  mountain  sheep  being  generally 
remarkably  agile. 

Of  the  wild  sheep  the  largest  number  belong  to  Asia  ; 


SHEEP-  GO  A  TS— ANTELOPES. 


but  the  Moufflon  lives  in  Corsica  and  Sardinia  ;  North 
Africa  has  a  large  and  handsome  species  in  the  Barbary 
sheep,  and  America  in  the  Big  Horn  of  the  Rocky 
Mountains.  All  the  wild  sheep  have  horns,  which  in 
some  kinds  reach  a  very  large  size. 

GOATS.— Closely  related  to  the  sheep,  and  really 
difficult  to  distinguish  from  them  in  some  species,  are 
the  Goats,  all  of  whom  are  horned  and  bearded.  They 
belong  exclusively  to  Europe,  North  Africa,  and  Asia. 
The  flesh  of  the  goat  is  not  so  highly  esteemed  as  that 


Mountain  Goat  or  Tbex. 

of  the  sheep,  but  their  milk  is  more  used,  and  the  hair 
of  the  Angora  and  Cashmere  goats  is  as  valuable  as  the 
sheep's  wool. 

ANTELOPES. — The  principal  home  of  the  great  Ante- 
lope   Family   is   in    Africa,    where   vast   herds  of  these 


64 


ANIMAL   AND   VEGETABLE  KINGDOMS. 


creatures  range  in  endless  variety  of  species,  varying  in 
size  from  the  Grand  Eland,  which  rivals  the  ox  in 
dimensions,  to  the  tiny  and  graceful  Gazelles,  barely  two 
feet  high.  We  read  in  African  travels  of  Steinboks, 
Springboks,  Bushboks,  Gemsboks,  Koodoos,  Hartebeests, 
and  many  others,  all  included  among  antelopes.  Some 
are  nearer  the  Ox  group,  others  more  like  goats,  while 


many  have  a  strong  resemblance  to  deer,  from  which, 
however,  they  are  clearly  distinguished  by  their  perma- 
nent hollow  horns.  Most  of  them  are  light,  active,  and 
graceful  in  their  movements,  and  the  little  Springbok, 
which  is  about  thirty  inches  in  height,  frequently  leaps 
into  the  air  to  a  height  of  from  seven  or  eight  to  as  much 
as  twelve  feet.  But  the  most  extraordinary  of  the  African 
antelopes  is  the  Gnu,  or  Wildebeest.  It  has  a  head  and 


THE   GIRAFFE.  65 

shoulders  not  unlike  a  bull,  while  its  hind  quarters  and 
tail  are  more  like  those  of  a  pony,  which  animal  it  also 


resembles  in  its  manner  of  wheeling,  prancing,  kicking, 
and  snorting. 

Several  species  of  Antelopes  are  found  in  Asia,  one 
in  California,  and  one  in  Europe,  the  pretty  little  Chamois 
of  the  Alps. 

GIRAFFES. — Next  to  the  Antelopes,  and  intermediate 
between  them  and  the  Deer,  is  placed  the  Giraffe,  which, 
instead  of  true  horns,  has  only  two  short  appendages  on 
the  head,  and  a  bony  lump  between  the  eyes,  all  of  which 
are  entirely  covered  by  the  skin. 

There  is  something  very  attractive  about  this  quaint, 
long-legged,  long-necked  creature,  which,  with  its  gentle 
eyes  and  awkward,  angular  movements,  so  vividly  suggests 
a  Noah's  ark  animal  of  wood  and  leather  as  to  give 

F 


66        ANIMAL  AND    VEGETABLE  KINGDOMS. 

rise  to  a  constant  wish  to  feel  it  and  make  sure  that  it 
is  real.  The  great  height,  some  sixteen  or  eighteen  feet, 
from  which  it  looks  down  on  us  should,  indeed,  inspire 
respect;  but  then  it  is  all  the  more  comical  when 
straddling  its  legs  apart  in  the  difficult  endeavour  to 
get  its  head  to  the  ground.  In  its  African  home  it 
feeds  habitually  on  the  leaves  of  trees,  selecting  and 
plucking  them  daintily  with  its  long  tongue.  It  is  a 
gentle,  timid,  and  affectionate  animal,  and  has  rarely 
been  heard  to  make  a  sound. 

DEER. — The  Deer  Family  are  distinguished  from  all 
others  by  the  remarkable  history  of  their  antlers.  These 
ornaments  belong  to  the  male  animal  only,  except  with 
the  reindeer,  whose  female  is  also  horned.  The  horns 
vary  greatly  in  size  and  in  the  number  and  kind  of 
branches  borne  by  different  species  and  at  different  ages, 


Antlers  of  deer  (1-5)  in  successive  years. 
From  Chambers's  Encyclopaedia. 

but  all  alike  are  shed  every  year.  In  each  year  of  a 
stag's  growth  its  antlers  grow  more  and  more  branched. 
The  Red  Deer,  which  are  still  found  wild  in  parts  of  the 
British  Islands,  lose  their  horns  in  the  spring  between 
February  and  May.  In  a  few  days,  however,  they  begin 


THE  DEVELOPMENT  OF  ANTLERS.  67 

sprouting  again,  and  all  the  time  they  are  growing  they 
are  covered  with  a  soft  furry  skin,  called  "  velvet,"  which 
is  hot  to  the  touch  from  the  rapid  coursing  of  the  blood 
in  it.  When  the  growth  of  the  horn  is  complete  for  the 
year,  this  skin  or  "  velvet "  dries  up,  and  is  gradually  worn 
off  by  the  animal  rubbing  its  head  against  the  trees  until 
only  the  hard  solid  horn  of  the  antler  remains.  In  its  first 
year  the  young  stag  grows  only  a  simple  spike  with  one 
point,  but  year  by  year  the  new  horns  increase  in  size 
and  complexity  until  the  full-grown  stag  over  six  years 
old,  carries  magnificent  antlers  with  points  varying  from 
sixteen  up  to  even  as  many  as  sixty-six.  But  the  whole 
of  this  growth  is  completed  in  a  very  short  time — about 
ten  weeks.  By  the  end  of  August  the  horns  are  cleared 
of  "  velvet,"  and  the  fully-armed  stag,  who  remained  in 
quiet  and  retirement  while  his  weapons  were  growing, 
comes  out  prepared  to  fight  the  world,  and  at  this  time 
of  year,  is  very  quarrelsome  and  dangerous.  The  stags 
fight  each  other  for  the  possession  of  the  does,  and 
not  infrequently  kill  each  other.  The  fawns,  which  are 
born  in  May  and  June,  are  brightly  spotted  with  white 
in  the  summer,  and  gradually  assume  the  red  colour  of 
the  full-grown  animal. 

In  those  kinds  of  deer  which  have  very  small  or 
simple  horns,  the  canine  teeth  are  developed  into  small 
tusks  as  if  to  balance  the  want  of  them,  and  there  are 
one  or  two  species  altogether  hornless,  such  as  the 
Musk  Deer,  and  the  Chinese  Water-deer,  in  which  the 
tusks  become  of  considerable  size. 

Deer  belong  chiefly  to  Europe  and  Asia ;  there  are 
a  few  in  America,  but  they  are  unknown  in  Africa  south 


68        ANIMAL   AND    VEGETABLE  KINGDOMS. 

of  the  Sahara,  where  their  place  seems  to  be  taken  by 
the  antelopes.  The  red  deer  and  the  roebuck  are 
natives  of  Britain,  though  now  driven  into  remote 
districts,  but  the  fallow  or  spotted  deer,  which  are 
most  frequently  seen  in  our  parks,  are  imported  from 
other  countries. 

The  largest  of  the  deer  is  the  Elk,  or  the  Moose  of 
North  America,  which  sometimes  stands  eight  feet  high 


Head  of  Reindeer. 


at  the   shoulder — as  high  as  a  fair-sized  elephant.     Its 
horns    are    "  palmated ; "    that    is,   their    branches    are 


THE  DEER  FAMILY.  69 

connected  together  by  sheets  of  bony  tissue,  making  the 
whole  pair  of  antlers  appear  like  a  huge  basin,  and 
adding  immensely  to  the  weight,  which  is  so  great  that 
one  wonders  how  the  animal  can  carry  such  a  burden. 
Nevertheless,  the  Moose  is  a  swift  and  powerful  runner, 
and  a  good  swimmer.  An  extinct  gigantic  deer,  the 
so-called  "  Irish  Elk,"  had  still  larger  antlers  than  the 
Moose. 

The  most  useful  to  man  of  the  Deer  Family,  is  the 
Reindeer  of  the  Arctic  Regions,  herds  of  which  con- 
stitute the  wealth  of  the  Laplanders.  This  is  a  powerful 
and  enduring  animal,  and  is  used  both  for  carrying  riders 
and  baggage,  and  drawing  sledges.  It  is  peculiarly 
fitted  for  travelling  over  snow,  as  the  two  sides  of  the 
hoof  part  widely  when  pressed  upon  the  ground,  and 
spread  so  much  as  to  give  the  same  sort  of  help  as  a 
snow-shoe.  Also  one  of  its  horns  has  generally  a  branch 
widely  expanded,  and  standing  straight  forward  just  over 
its  brow  (see  picture),  which  serves  as  a  snow-plough  to 
shovel  aside  the  snow,  under  which  its  food,  consisting 
in  winter  principally  of  a  dry  sort  of  lichen,  is  concealed. 

CHEVROTAINS. — After  the  Deer  come  a  family  known 
as  the  Chevrotains,  which  are  wee,  pretty  Deerlets,  about 
as  big  as  a  rabbit  or  hare,  with  large  dark  eyes  and  a 
gentle  and  confiding  expression.  They  differ  from  the 
true  deer  in  having  no  horns,  but  tusks  large  enough 
to  show  outside  when  the  mouth  is  shut ;  and  also  the 
bones  of  the  feet  approach  in  some  respects  more  nearly 
to  those  of  the  swine.  These  graceful  little  creatures 
belong  to  Southern  Asia  and  West  Africa. 

The  whole  of  the  Ruminating  animals  hitherto  spoken 


70        ANIMAL  AND    VEGETABLE  KINGDOMS. 

of  are  distinguished  by  having  front  teeth  only  in  the 
lower  jaw,  the  upper  front  teeth  being  replaced  by  a 
horny  sort  of  pad  against  which  the  lower  teeth  bite,  and 
which  helps  to  lay  hold  of  and  tear  off  the  green  food 
on  which  they  live.  The  sound  of  this  tearing  up  the 
grass  is  very  noticeable  when  a  herd  of  cattle  or  sheep 


are  grazing  together.  But  the  Camels  and  Llamas, 
though  they  are  also  Ruminants,  have  two  upper  front 
teeth. 

CAMELS. — Camels  have  been  kept  for  use  by  dwellers 
in  the  East  from  the  earliest  times,  and  formed  part  of 
the  wealth  of  Abraham.  Their  broad  cushioned  feet, 
well  adapted  for  travelling  over  the  desert  sands,  great 
endurance,  power  of  subsisting  on  small  quantities  of  the 
dryest  shrubs,  and  of  storing  several  days'  supply  of 
water  in  their  stomachs,  render  them  invaluable  to 
Eastern  travellers.  They  stand  about  six  or  seven  feet 
high  at  the  shoulder,  and  are  of  a  light  brown  colour, 


THE   CAMEL.  7  I 

closely  resembling  that  of  the  desert  sand  itself.  To  be 
loaded  or  unloaded  the  camels  kneel  down,  and  this  is 
also  their  attitude  of  rest,  their  weight  being  supported 
in  that  position  upon  thick  pads  with  which  the  knees 
and  breast  are  furnished. 

Their  long  soft  lips,  the  upper  one  of  which  is  split 
up  in  the  centre,  and  their  slit-like  nostrils,  give  them  a 
curious  expression  of  countenance ;  but  the  most  remark- 
able point  about  the  camel  is  the  hump,  which  acts  as 
a  reserve  store  of  nourishment,  being  large  and  plump 
when  the  animal  is  well  fed,  and  gradually  absorbed 
during  a  long  journey  with  scanty  food.  The  Arabian 
Camel,  which  is  found  throughout  North  Africa,  and  as 
far  east  as  India,  and  the  Dromedary,  a  lighter  and 
swifter  variety  of  the  same,  have  only  one  hump ;  but 
the  Bactrian  Camel,  a  native  of  more  northern  districts 
of  Asia,  has  two.  The  humps  are  soft  and  flexible,  and 
blow  to  one  side  in  a  wind.  In  our  recent  North  African 
campaigns  a  Camel  corps  was  raised  for  the  work  in 
the  desert ;  no  new  feature  in  war,  for  we  hear  that,  in 
David's  Amalekite  raid,  "  there  escaped  not  a  man  of 
them,  save  four  hundred  young  men,  which  rode  upon 
camels,  and  fled"  (i  Sam.  xxx.  17). 

All  the  Camels  bear  a  bad  character  with  those  who 
know  them  well.  They  are  described  by  a  traveller  as 
"  great,  grumbling,  groaning,  brown  brutes  ; "  and  he  adds, 
"  never  do  I  remember  to  have  seen  a  camel  in  a  good 
humour." 

LLAMAS. — In  the  New  World  the  Camels  are  replaced 
by  the  Llamas  of  South  America,  animals  of  the  same 
family,  but  much  smaller,  the  largest  not  exceeding  three 


72         ANIMAL  AND    VEGETABLE  KINGDOMS. 


feet  six  inches  at  the  shoulder,  without  humps,  without 
the  broad  cushions  of  the  feet,  and  with  more  sheep-like 
faces.  They  have  a  very  unpleasant  habit,  when  annoyed, 
of  discharging  the  contents  of  their  mouths  over  the 
offender,  and  have  been  known  in  this  way  to  rid  them- 
selves of  their  riders  when  tired  of  carrying ;  but  they 
are  now  rarely  used  as  beasts  of  burden.  The  wool  of 


these  creatures  is  long  and  silky,  and  under  the  names 
of  Llama,  Alpaca,  and  Vicuna,  according  to  the  species, 
is  well  known  in  manufactures. 

On  looking  back  over  the  numerous  Families  of  this 
great  Order  it  is  interesting  to  see  that  in  the  Bible 
history  notice  had  been  taken  of  their  main  divisions, 
and  the  only  animals  reputed  clean  for  food  for  the 
Israelites  were  the  cloven-hoofed  ruminants.  "  Whatso- 
ever parteth  the  hoof,  and  is  cloven-footed,  and  cheweth 
the  cud,  among  the  beasts,  that  shall  ye  eat.  The 


RODENTS.  73 

camel,  because  he  cheweth  the  cud,  but  divideth  not 
the  hoof;  he  is  unclean  unto  you.  And  the  swine, 
though  he  divide  the  hoof,  and  be  cloven-footed,  yet  he 
cheweth  not  the  cud ;  he  is  unclean  unto  you "  (Lev.  xi. 

3.  4,  ?)• 

We  do,  in  fact,  reckon  the  camel  among  the  cloven- 
footed,  but  the  division  of  the  foot  is  less  marked  than 
with  some  of  the  Order. 

Rodents  (Rodentia). — We  come  now  to  an  Order  of 
animals  small  in  size,  but  immensely  prolific  in  numbers, 
and  very  distinctly  marked  off  from  all  others,  which  are 
aptly  known  as  Rodents,  or  Gnawing  creatures.  They 
have  two  long  front  teeth  above  and  two  below,  with  a 
considerable  gap  between  these  and  the  back  teeth  or 
grinders,  and  no  canines  at  all.  But  their  peculiarity  is 
that  the  long  front  teeth  are  always  growing  and  are 
only  kept  to  a  reasonable  size  by  constant  use.  Gnaw 
they  must,  or  they  will  die;  and  instances  abound  in 
which  by  the  accidental  loss  of  a  tooth,  the  opposite 
tooth  which  should  have  been  ground  down  by  it  has 
grown  on  right  through  the  other  jaw  till  the  poor 
creature  could  no  longer  open  and  shut  its  mouth,  and 
has  died  of  starvation. 

The  Rodents  consist  of  four  main  groups,  the  Squirrels, 
the  Rats  and  Mice,  the  Porcupines,  and  the  Hares  and 
Rabbits. 

SQUIRRELS. — Our  pretty  little  English  squirrel  is  a 
good  example  of  its  Family.  With  its  large  bushy  tail 
cocked  up  over  its  back,  its  bright  eyes,  quick,  lively, 
and  playful  movements,  scampering  up  and  down  trees, 
taking  flying  leaps  from  one  to  another,  challenging 


74        ANIMAL   AND    VEGETABLE  KINGDOMS. 

its  companions  to  race,  or  sitting  up  nibbling  a  nut 
held  between  its  fore  paws,  it  is  one  of  the  most 
captivating  of  our  wild  animals.  It  is  eight  or  ten 
inches  in  length,  the  tail  adding  seven  or  eight  more 
inches ;  it  has  hind  legs  much  longer  than  the  fore 
legs,  and  is  in  summer  of  a  red-brown  colour  above 
and  white  below,  becoming  greyer  in  winter.  It  is 


Flying  Squirrel. 

a  prudent  little  creature,  and,  when  food  is  abundant, 
lays  by  stores  for  winter  use,  for  though  it  sleeps  away 
much  of  the  winter,  yet  it  rouses  from  time  to  time  to 
satisfy  its  hunger.  Squirrels  of  different  species  are  dis- 
tributed over  almost  'all  the  world,  and  a  large  group  of 
them,  the  Flying  Squirrels,  have  a  deep  fold  of  skin 
stretching  along  each  side  of  the  body,  connecting  the 
fore  and  hind  legs,  which  is  widely  extended  when  they 


THE  SQUIRREL   GROUP.  75 

are  jumping,  and  serves  to  support  them  in  the  air  like 
that  of  the  Colugo,  or  Flying  Lemur.  One  of  the  Flying 
Squirrels,  the  wee  little  Assapan  of  North  America,  does 
not  measure  more  than  four  and  three-quarter  inches  in 
length  without  the  tail.  In  America  also  are  found  most 
of  the  Ground  Squirrels,  which,  instead  of  building  their 
nests  in  trees,  burrow  into  the  ground;  and  these  lead 
by  an  easy  connection  to  their  relations  the  Marmots, 
which  are  not  unlike  squirrels  with  very  poor  tails.  The 
Alpine  Marmot  of  Europe  is  large  for  a  Rodent, 
measuring  twenty  inches  to  the  root  of  the  tail,  but  the 
most  interesting  of  the  set  is  the  Prairie  "  Dog  "  of  North 
America,  so  called  from  its  little  quick  cry  like  the 
barking  of  a  small  dog.  The  Prairie  "  Dogs  "  live  together 
in  great  numbers  and  their  burrows  are  as  thickly  con- 
gregated as  those  in  any  rabbit  warren,  while  in  front  of 
the  mouth  of  each  is  thrown  up  a  hillock  of  the  excavated 
earth,  on  which  the  occupant  habitually  sits.  It  is  a  quaint 
sight  to  see,  from  the  railway  trains  running  through 
the  prairies,  these  hillocks,  clustered  by  hundreds,  each 
with  a  little  animal  seated  on  the  top  of  it.  Another 
very  curious  feature  of  a  "  Dog  town,"  as  it  is  called,  is 
that  the  burrows  are  constantly  shared  with  a  kind  of 
small  Owl,  known  as  the  Burrowing  Owl,  about  the  last 
creature  one  would  expect  to  find  underground,  and 
sometimes  a  less  welcome  guest  appears  in  the  Rattle- 
snake, which  feeds  upon  the  young  "  dogs." 

To  the  Squirrel  Group  also  is  referred  that  intelligent 
carpenter  and  builder,  the  Beaver,  which  haunts  the 
rivers  of  North  America,  having  now  almost  entirely 
disappeared  from  Europe,  where  it  used  to  be  plentiful. 


76        ANIMAL  AND    VEGETABLE  KINGDOMS. 


Beavers  are  about  two  and  a  half  feet  long,  with 
a  flattened  trowel-like  tail,  and  webbed  hind-feet. 
They  live  together  in  communities,  building  their  strong 
lodges  in  the  water,  and  for  this  purpose  they  actually 
cut  down  trees  by  gnawing  round  and  round  the 
trunk  with  their  powerful  teeth.  The  trees,  some  of 
which  have  been  measured  not  less  than  eighteen  inches 


Ifxi 


in  diameter,  are  neatly  cut  into  logs  about  five  feet  long, 
and  then  built  one  upon  another  with  a  plaster  of  mud. 
The  dwellings,  when  complete,  stand  out  above  the  top 
of  the  water,  but  the  entrances  are  always  under 
water,  and  if  the  beavers  cannot  find  a  sufficiently  deep 
pool  for  their  needs  they  build  in  the  same  way  a  dam 
across  the  stream,  to  pen  back  a  good  height  of  water. 
Some  of  these  engineering  works  are  of  astonishing  size, 


RATS  AND  MICE.  77 

beaver  dams  having  been  seen  three  hundred  yards  long, 
and  ten  or  twelve  feet  wide  at  the  bottom,  narrowing  up 
to  the  top  of  the  water. 

RATS  AND  MICE. — Whatever  other  animals  may  be 
strange  to  us,  we  are  all  familiar  enough  with  rats  and 
mice,  and  probably  regard  them  with  no  friendly  feelings, 
from  their  habits  of  making  themselves  at  home  without 
invitation,  and  making  free  with  all  eatable  property 
alike  in  our  houses,  ships,  barns,  ricks,  and  in  the  open 
fields.  They  are  found  in  all  parts  of  the  world  and  in 
many  species,  but  our  domestic  rats  and  mice  are  cha- 
racteristic types  of  the  whole  group. 

The  common  Brown  Rat  is  a  masterful  creature,  and 
allows  no  other  species  to  remain  where  he  has  taken 
possession,  so  that  he  has 
partially  exterminated  the 
Black  Rat  which  formerly 
abounded  in  this  country. 
Although  every  one's  hand 
is  against  the  rats,  yet  they 
hold  their  own,  partly 
through  the  extraordinary 
rate  at  which  they  multiply, 
breeding  several  times  a 
year,  with  from  ten  to  four- 
teen young  in  each  litter, 
partly  through  their  power 

of  acting  together.  They  will  eat  anything,  and  their 
disposition  varies  with  their  food,  but  those  that  fre- 
quently get  animal  food  (like  the  sewer  rats  in  our 
towns)  are  fierce  creatures,  and,  when  hungry,  positively 


ANIMAL  AND    VEGETABLE  KINGDOMS. 


dangerous.  A  large  party  of  famishing  rats  would  soon 
pull  down  a  man,  and  even  a  single  rat  will  sometimes 
attack  a  young  child.  However,  even  these  unpleasant 
animals  have  their  use  in  devouring  offal  and  other 
pestilence-breeding  matters  thrown  into  the  sewers ;  and 
the  country  rats  are  quite  content  with  stealing  vegetable 
food. 

The  audacious  little  mice  imitate  their  bigger  cousins 
in  the  matter  of  thieving ;  and  they  are  also  very  wary 
creatures,  soon  understanding  and  avoiding  a  trap  which 
has  been  several  times  set  for  them.  Mice  are  un- 
doubtedly fond  of  music,  and  individuals  among  them 
have  some  power  of  singing  and  even  of  imitating  the 
song  of  a  special  bird.  They  are  quite  as  prolific  as  rats. 
The  Dormouse  and  the  tiny  Harvest  Mouse,  only  five 
inches  in  total  length,  are 
attractive  little  creatures, 
and  the  Harvest  Mouse 
makes  a  beautiful  cradle 
for  its  little  ones  of  grass 
blades  woven  together  into 
a  hollow  ball  about  the 
size  of  a  cricket-ball,  which 
is  slung  between  the  stems 
of  the  growing  grass  by 
using  some  of  the  blades 
as  they  grow,  without  de- 
taching them. 

One  of  the  most  remark- 
able of  the  rat  group  is  the  active  little  Jerboa  or 
Jumping  Mouse  of  the  African  and  Arabian  deserts. 


boa. 


THE  PORCUPINE.  79 

It  is  six  inches  long,  with  about  eight  inches  more  in 
the  tail,  and  its  special  distinction  is  the  disproportionate 
length  of  the  hind  legs.  As  it  walks  and  jumps  only 
on  these,  carrying  the  short  fore  paws  pressed  close  to 
its  breast,  it  has  very  much  the  air  of  a  bird  hopping. 

PORCUPINES. — The  peculiar  feature  of  the  Porcupine 
is  the  number  of  stiff  bristles,  spines,  and  quills  mixed 
with  its  hair  :  and  when  it  is  irritated,  and  sets  these  up 
on  end,  it  presents  a  formidable  appearance.  Its  mode 


Porcupine. 

of  attack  is  by  backing  upon  its  enemy  with  the  points 
of  its  quills,  and  as  the  quills  are  loosely  attached  to  the 
skin,  and  readily  come  out  when  touched,  they  remain 
in  the  flesh  of  the  opponent  and  make  severe  wounds. 
A  tiger  has  been  found  with  porcupine  quills  sticking  in 
its  paws  and  head.  The  common  porcupine  is  from 
thirty  to  thirty-six  inches  in  total  length,  and  is  an  inhabi- 
tant of  South  Europe  and  North  Africa.  Other  like 
species  are  found  in  Asia,  while  the  American  porcupines 
are  different  in  their  habits  and  live  in  trees. 

To  the  Porcupine  group  belong  a  number  of  small 


80        ANIMAL  AND    VEGETABLE   KINGDOMS. 

rodents — Chinchillas,  rather  like  squirrels  with  very  soft, 
grey  fur ;  Agoutis,  small,  slender-limbed  pig-like  creatures, 
very  quick  and  active  in  running  and  springing,  which 
do  great  damage  in  the  sugar  plantations  of  South 
America ;  and  Cavies,  of  which  the  best  known  in  this 
country  is  the  dull  little  tailless  guinea-pig.  In  their 
South  American  home,  however,  much  larger  kinds  of 
Cavy  are  to  be  found,  and,  indeed,  the  Capybara,  or 
Water  Pig,  the  largest  of  the  Rodents,  measuring  four 
feet  in  length,  belongs  to  this  Family. 

HARES  AND  RABBITS. — The  Hares  and  the  Rabbits 
form  a  single  family  belonging  to  the  fourth  group,  and 
there  is  a  great  general  resemblance  between  them,  but 
the  hind-legs  of  hares  are  nearly  twice  as  long  as  the 
fore-legs,  while  there  is  much  less  difference  between 
those  of  rabbits  :  the  hares'  ears,  also,  are  much  longer 
in  proportion.  Hares  live  on  the  ground,  concealing 
themselves  among  the  grass :  rabbits  burrow  under- 
ground. Young  hares  are  born  with  their  eyes  open, 
and  clothed  with  hair,  while  rabbits  are  born  blind 
and  naked.  They  all  feed  principally  in  the  twilight, 
but,  while  the  hare  loves  to  lie  quiet  in  the  daytime, 
the  little  rabbits  are  constantly  engaged  in  comical  play 
together  near  their  burrows.  They  are  native  in  almost 
every  part  of  the  world  except  Australia,  and  rabbits 
have  been  introduced  there  in  recent  years ;  they  have 
multiplied  exceedingly  and  become  a  great  nuisance  to 
the  colonists. 

Edentata. — The  next  Order  is  a  complete  contrast 
to  the  last ;  for,  whereas  the  rodents  are  characterized 
by  their  large  strong  front  teeth,  these  have  no  front 


TOOTHLESS   CREATURES. 


8l 


teeth  or  canines,  and  some  of  them  have  no  teeth  at  all, 
from  which  they  get  their  name  of  Edentata,  or  toothless. 
They  belong  entirely  to  tropical  countries,  and  include 
some  of  the  oddest  beasts  living  on  the  earth. 

SLOTHS.— The  first  group  of  them  are  the  Sloths,  hairy 
animals,  without  tails,  about  two  feet  long,  with  three 
toes  on  the  hind-feet,  and  either  two  or  three  on  the 


Sloth. 

fore  feet,  all  armed  with  long  sharp  curved  claws.  Their 
special  peculiarity  is  that  they  spend  their  lives  clinging 
to  the  under-side  of  tree  boughs  :  they  travel  in  this  way 
from  tree  to  tree  upside  down,  they  eat  upside  down,  they 
sleep  upside  down.  But  to  counterbalance  the  awkward- 
ness of  this  position  they  have  an  extraordinary  power  of 


82         ANIMAL   AND    VEGETABLE  KINGDOMS. 

turning  their  heads  right  round,  so  as  to  look  at  anything 
behind,  or  beneath  them.  If  placed  upon  the  ground 
they  drag  themselves  slowly  and  awkwardly,  not  upon 
their  front  paws,  but  upon  their  elbows,  to  the  nearest 
tree,  or  anything  they  can  hang  to.  In  the  trees  they 
move  faster,  but  are  never  very  nimble,  and  spend  much 
of  their  time  in  sleep,  feeding  chiefly  at  night  on  leaves 
and  twigs.  They  belong  to  Central  and  South  America. 
ANT-EATERS. — Next  come  the  Ant-eaters,  which  are 
strangely  various  in  shape  and  appearance.  They  all 


have  very  long,  round,  worm-like  tongues,  which  can  be 
thrust  far  out  of  the  mouth,  and  which  wriggle  as  if  they 
had  an  independent  life,  but  this  almost  seems  the 
end  of  their  likeness.  The  Tamandua  and  the  two- toed 
ant-eater  of  South  America  are  not  unlike  sloths  with 
long,  useful  tails,  which  they  twist  round  branches  to 
hold  on  by  like  the  American  monkeys.  Then  we 
have  the  Great  Ant-bear  of  South  America,  the  oddest 
of  all.  It  has  a  very  long  narrow  head,  a  still  longer 


ANT-EATERS.  83 

tongue,  a  long  neck,  and  is  in  all  about  four  and  a  half 
or  five  feet  long  to  the  root  of  the  tail ;  but  then  comes 
at  least  three  feet  more  of  tail,  and  such  a  tail— huge, 
bushy,  plumy — making  a  complete  shelter  from  the  sun 
when  the  owner  turns  it  over  his  back,  and  lies  down 
under  his  own  shadow.  He  is  a  slow,  stupid  animal  • 
but  when  very  hard  pressed  will  sit  up  and  endeavour, 
like  a  bear,  to  squeeze  his  enemy  to  death  in  his  grasp. 

Except  the  Tamandua  and  its  relations,  which  hunt 
for  insects  under  the  bark  of  the  trees,  all  these  creatures 
live  by  scratching  down  the  sides  of  great  ant-hills  with 
their  powerful  claws,  and  laying  their  long  sticky  tongues 
among  the  ants,  which  adhere  to  them,  and  are  thus 
drawn  into  the  mouth  of  the  ant-eaters. 

The  CAPE  ANT-EATER  from  Africa,  which  belongs  to 
quite  a  distinct  family,  more  nearly  resembles  a  pig,  if 
we  can  imagine  a  pig  five  feet  long,  including  its  twenty 


inches  of  tail,  without  teeth,  with  a  tongue  like  a  worm, 
and  with  long  pointed  ears  like  a  hare.  A  third  set, 
the  PANGOLINS,  or  Scaly  Ant-eaters,  form  another  distinct 


84        ANIMAL  AND    VEGETABLE  KINGDOMS. 

family.  They  are  covered  all  over  with  a  complete  armour 
of  large,  horny,  pointed  scales,  overlapping  each  other 
like  tiles,  with  their  pointed  ends  towards  the  tail. 
These  extraordinary  creatures  vary  from  two  to  five 
feet  in  length,  most  of  which  is  in  the  tail,  and  when 
attacked,  roll  themselves  up  so  as  to  protect  their  heads 
under  their  armour,  and  set  up  the  sharp  edges  of  their 
scales  towards  the  enemy.  They  are  found  both  in 
Africa  and  in  Southern  Asia,  and  are  absolutely  without 
teeth. 

ARMADILLOS. — The   Armadillos,   the   last    Family   of 
the  Edentata,  all  belong  to  South  America,  and  are  dis- 


tinguished by  the  hard  bony  shields,  like  those  of 
Crocodiles,  which  cover  the  upper  side  of  their  bodies 
and  heads.  They  vary  in  size  from  fourteen  inches  to 
over  three  feet,  and  have  round  bodies,  short  legs,  and 
large,  strong  claws,  with  which  they  burrow  rapidly  into 
the  earth.  They  are  quick  runners,  will  eat  anything, 
and  are  themselves  very  good  to  eat.  One  small  species, 
the  Ball  Armadillo,  has  the  power  of  rolling  itself  up, 


POUCHED  ANIMALS.  85 

and  thus  baffling  the  monkeys,  who  love  to  drag  back 
an  Armadillo  by  the  tail  as  it  runs  to  its  burrow,  but  who 
can  make  nothing  of  a  ball  with  nothing  to  pull  at,  and 
too  large  to  be  cracked.  It  makes  a  beautiful  ball,  the 
neat  fit  of  its  shields  being  only  rivalled  by  the  beauty  of 
their  ornamentation. 

Marsupials  (Manupialia). — Pouched  animals.  The 
next  Order  of  the  Mammals,  which  belongs  almost  ex- 
clusively to  Australia  and  the  neighbouring  islands,  is 
a  very  interesting  study,  for  it  appears  to  include  animals 
closely  resembling  members  of  many  families  already 
described,  Cats,  Dogs,  Bears,  Squirrels,  Rats,  Hares,  etc. ; 
but  the  Australian  forms  of  these  creatures  are  dis- 
tinguished by  a  peculiarity  so  marked  that  all  who 
possess  it  must  be  referred  to  one  Order.  This  peculiarity 
is  the  history  of  the  birth  and  nourishment  of  the  young. 

KANGAROO. — The  Kangaroo  is  the  typical  animal,  the 
description  of  which  will  best  serve  to  introduce  this 
leading  feature  of  the  whole  Order. 

The  male  of  the  Great  Kangaroo  is  a  very  large 
animal,  clothed  in  thick  warm  fur  of  a  greyish  brown 
colour,  with  a  gentle-looking  face,  large  full  eye,  and 
upright  ears.  Its  limbs  appear  much  out  of  proportion, 
for  the  fore-legs  are  short,  while  the  hind  limbs  are  very 
long,  large,  and  strong,  the  great  hind  feet  sometimes 
nearly  as  long  as  the  leg  bone,  and  armed  with  claws, 
one  of  which  is  larger  than  the  rest,  and  a  truly  formidable 
weapon.  When  moving  slowly  or  feeding,  the  Kangaroo 
goes  on  all  fours,  with  an  awkward  gait ;  but  when  speed 
is  required  the  hind  legs  alone  are  used,  and  the  animal 
progresses  by  great  leaps,  clearing  often  fifteen  feet  or 


86        ANIMAL   AND    VEGETABLE  KINGDOMS. 


more  at  every  bound,  and  distancing  even  good  horses. 
It  habitually  sits  or  stands  upright,  supporting  itself  on 
the  hind  legs  and  great  tail,  and  in  this  attitude  often 
reaches  the  full  height  of  a  man. 

Though  the  front  limbs  are  short  they  are  capable 
of  much  more  varied  movement  than  those  of  many 
creatures,  and  may  almost  be  called  arms.  They  can 
be  turned  freely  on  the  elbow  like  a  man's  arm,  can  be 


'•''.',  ''•' i< 


Kangaroo. 

moved  up  and  down,  or  put  behind  the  back,  and  the 
paw  can  grasp,  hold,  or  pick  up  things  like  a  hand. 

The  Kangaroo  will  run  away  from  a  hunter  if  it  can, 
but  if  hard  pressed  will  fight  to  the  last,  and  is  not  to 
be  trifled  with,  as  one  blow  of  its  powerful  hind  claws 
can  rip  open  the  body  of  a  dog.  When  turned  to  bay 
by  dogs  near  water  it  has  been  known  to  seize  a  dog 
in  its  arms,  hop  off  to  the  water,  and  hold  it  under  water 
till  it  is  drowned. 


CURIOUS  CREATURES.  87 

The  female,  who  is  much  smaller,  carries  the  distinctive 
mark  of  the  Order,  a  large  outside  pouch  of  skin  on  the 
lower  part  of  the  body.  When  the  young  Kangaroo  is 
born,  it  is  very  tiny  and  in  very  undeveloped  condition, 
hardly  more  than  an  inch  long,  colourless,  and  almost 
transparent.  The  mother  immediately  places  it  in  her 
pouch,  containing  the  teats,  to  one  of  which  it  attaches 
itself;  and  in  this  living  cradle  it  dwells  and  grows  for 
eight  months,  until  it  is  able  to  take  care  of  itself.  As 
it  grows  larger,  it  may  be  seen  peeping  out  of  the  pouch ; 
and  even  when  able  to  come  out  and  feed  on  the  grass, 
it  still  runs  back  to  its  shelter  for  rest  and  safety,  until 
it  reaches  a  weight  of  about  ten  pounds,  when  the  mother 
finally  turns  it  out. 

There  are  many  species  of  Kangaroo,  varying  in  size 
and  in  details,  and  to  the  same  Family  belong  the 
Kangaroo  Hare,  and  the  Kangaroo  Rats,  or  Potoroos, 
which  are  about  as  large  as  rabbits,  and  have  heads  and 
teeth  somewhat  like  rodents. 

Among  the  many  other  curious  creatures  of  the  Order, 
must  be  mentioned  the  Wombat,  a  burrowing  animal, 
with  round  fat  body  two  or  three  feet  long,  a  stumpy 
tail,  short  equal  limbs,  heavy  waddling  gait,  and  a 
singularly  placid  and  apathetic  disposition ;  the  Koala, 
or  Australian  "  bear,"  a  little  bear-like  tailless  creature 
with  thick  fur,  which  early  transfers  its  young  one  from 
the  pouch  to  its  back,  and  habitually  carries  it  there ;  the 
Cuscus,  somewhat  resembling  a  Lemur,  with  long  pre- 
hensile tail ;  and  the  Phalangers,  some  of  whom  have  a 
close  likeness  to  the  Flying  Squirrels.  The  cats  find 
their  Marsupial  representative  in  the  Ursine  Dasyure  or 


88        ANIMAL  AND    VEGETABLE   KINGDOMS. 

Native  Devil  of  Tasmania,  a  savage  little  creature  which 
commits  great  havoc  among  poultry  and  small  animals  ; 
and  the  dogs  in  the  Thylacinus  or  Zebra  Wolf,  also  a 
Tasmanian  animal  which  attacks  and  hunts  down  sheep. 
Both  these  creatures  have  great  canine  teeth,  and  other 
points  of  likeness  to  the  Carnivora. 

The  only  Marsupial  animals  found  outside  the  Australian 


Opossum,  with  young  on  her  back. 

district  are  the  stout  furry  Opossums  of  America,  the 
largest  of  which  is  equal  to  a  large  cat  in  size,  and  the 
smallest  not  exceeding  five  inches  without  the  tail. 
Their  tails  are  a  great  feature— long,  round,  flexible  — 
now  holding  on  to  the  branches  to  steady  their  owners 
in  their  bird's-nesting  excursions,  now  supporting  their 
whole  weight  as  they  hang  from  a  bough,  and  again 
arched  over  a  mother's  back  with  the  tails  of  a  whole 


EGG-LA  YING  ANIMALS. 


89 


young  family  twisted  round  it  to  secure  their  safe  seat 
as  they  ride.  The  Opossum  will  eat  anything,  and  is 
much  hunted,  both  on  account  of  its  depredations  among 
poultry,  and  for  the  value  of  its  fur. 

Egg-laying  Mammals  (Monotremata). — The  list  of 
the  Mammals  closes  with  an  order  which  may  really  be 
considered  a  sort  of  link  between  other  mammals  and 
reptiles.  The  best  known  member  of  this  very  remark- 
able group  is  a  flattish  animal,  reaching  at  most  eighteen 


Duck-billed  Platypus  (.Ornit/iorkyncJius), 

inches  in  length,  with  a  broad,  flat  tail,  like  a  beaver, 
flat,  webbed  feet,  furnished  with  claws,  the  web  of 
which  is  folded  back  when  the  claws  are  used  for 
digging ;  and  in  place  of  a  snout  a  broad  bill,  like  that 
of  a  duck,  which,  duck-like,  it  thrusts  into  the  mud, 
searching  for  food,  and  from  which  it  takes  its  name  of 
Duck-billed  Platypus.  Its  burrows  are  made  in  the 
banks  of  streams  and  pools,  the  entrances  to  them  being 
always  under  water;  and  much  of  its  life  is  passed  in 


QO        ANIMAL  AND    VEGETABLE  KINGDOMS. 

the  water,  but  it  can  also  run  on  land  and  even  climb. 
A  gentleman  who  has  kept  them  in  captivity  says  that 
they  are  very  cleanly  in  their  habits,  tending  their  fur 
as  carefully  as  cats,  and  that  the  young  are  very  lively 
and  playful. 

The  Spiny  ant-eaters  (Echidna)  agree  with  the 
Platypus  in  their  general  structure,  and  in  the  young 
being  hatched  from  eggs,  not  born  alive.  They  are, 
however,  very  different  outwardly,  being  provided  with 
a  long  pointed  "  beak,"  and  covered  with  short,  strong 
spines.  Both  the  Platypus  and  Echidnas  are  found  in 
Australia  and  Tasmania,  and  Echidnas  in  Papua  as  well. 

All  the  known  Mammalia  are  included  by  naturalists 
under  one  or  other  of  the  fourteen  Orders  described 
above ;  but  in  classifying  and  arranging  animals,  attention 
is  always  chiefly  directed  to  the  examination  of  the  bony 
skeleton,  rather  than  to  the  outward  appearance,  so  that 
without  a  good  deal  of  study  it  is  not  always  easy  to 
see  the  reasons  why  certain  animals  are  reckoned  in  one 
family  rather  than  another.  It  is  noticeable  that  among 
the  lower  species  of  the  Edentata,  the  Marsupials,  and 
the  Monotremes  which  are  purposely  set  last  in  the 
series,  some  details  of  the  skeleton  show  an  approach 
to  characters  which  belong  more  generally  to  birds  or 
to  reptiles,  and  so  fitly  lead  to  the  consideration  of  these 
other  great  classes  of  the  Vertebrate  Animals. 


CHAPTER    IV. 

BIRDS  (Aves). 

BIRDS,  which  form  the  second  class  of  the  Vertebrate 
Animals,  have  several  distinguishing  characters,  marking 
them  off  very  clearly  from  all  other  creatures.  They 
do  indeed  share  with  Mammals  their  red,  warm  blood, 
being,  in  fact,  hotter  than  the  Mammals  themselves,  but 
from  these  they  are  entirely  separated  by  their  hatching 
out  of  eggs ;  and  their  clothing  of  feathers  and  possession 
of  horny  beaks  are  easily  recognized  outward  characters 
which  belong  to  Birds  alone.  But  the  great  privilege 
of  birds  is  the  power  of  flight,  for  the  sake  of  which 
their  forelimbs  are  modified  into  wings.  Their  bodies 
contain  air-chambers,  and  even  the  bones  in  many  birds 
have  cavities  filled  with  air.  It  is  true  that  there  are 
birds,  like  the  ostrich,  which  cannot  fly,  perhaps  having 
lost  the  power  through  long  disuse,  but  still  the  wings 
exist  in  a  small  and  stunted  form,  showing  that  the  same 
ground  plan  runs  through  the  whole  Class. 

Birds  annually  shed  and  renew  their  feathers,  but  they 
lose  them  gradually,  so  that  though  they  pass  through 
a  time  of  shabby  plumage  at  the  moulting  season  they 
never  become  actually  bare.  They  vary  much  in  their 
powers  of  voice  ;  some  birds  uttering  only  harsh  screams, 


92        ANIMAL   AND    VEGETABLE  KINGDOMS. 

or  twittering  or  chattering  sounds,  while  others,  chiefly 
belonging  to  one  Order,  fill  the  air  with  their  musical 
songs. 

Another  most  notable  thing  in  many  birds  is  the 
extraordinary  instinct  of  migration  every  year  from  one 
climate  to  another.  It  is  indeed  only  made  possible  by 
their  power  of  flying  over  the  sea,  but  it  is  wonderful 
how  unerringly  they  guide  themselves  from  land  to  land, 
many  of  our  bird  friends,  after  wintering  in  Africa,  re- 
turning even  to  the  same  nest  which  they  built  here  the 
previous  summer.  Among  the  most  noticeable  of  our 
summer  visitors  are  the  cuckoo,  the  swallow,  and  the 
nightingale,  but  the  migratory  instinct  is  found  in  birds 
belonging  to  almost  every  Order.  The  whole  subject 
of  the  migrations  of  birds  is  far  from  being  well  under- 
stood, and  many  more  observations  are  needed.  There 
is  indeed  much  of  all  kinds  still  to  be  learnt  even  about 
our  most  ordinary  birds,  and  any  one  who  will  observe 
closely  and  record  accurately  what  comes  in  his  way, 
can  be  of  service  in  adding  to  our  knowledge. 

The  young  of  birds  are  hatched  out  of  eggs,  the  part 
of  the  egg  which  develops  into  the  young  bird  being  a 
tiny  germ  speck.  If  an  egg  is  laid  on  its  side,  the  germ 
spot  is  always  in  the  middle  of  the  upper  side,  and  may  be 
seen  by  breaking  open  the  shell  at  that  point.  It  can  be 
preserved  alive  for  a  short  time  in  the  same  condition,  but 
will  only  develop  into  a  living  bird  under  the  influence 
of  continued  heat.  This  heat  is  generally  supplied  by  the 
mother  bird  sitting  on  the  eggs ;  but  some  kinds  are 
hatched  by  the  heat  of  the  sun,  or  by  being  buried  in 
heaps  of  decaying  vegetable  matter — hot-beds,  in  fact. 


SECTION  OF  EGG  AT  THREE  STAGES.         93 


After  9  days. 


94        ANIMAL  AND    VEGETABLE  KINGDOMS. 

The  rapid  growth  in  the  egg  is  marvellous  to  think  cf. 
By  the  end  of  the  first  day's  sitting,  the  germ  has  become 
elongated  and  grooved,  the  brain  and  spinal  cord  of  the 
young  bird  forming  along  the  groove;  on  the  second 
day  the  heart  appears ;  by  the  third  bloodvessels  have 
been  formed,  and  so  the  little  chick  grows  on,  supported 
by  the.  yolk  of  the  egg  which  is  gradually  absorbed,  until 
within  three  weeks  the  tiny  germ  spot  is  changed  into 
a  complete  bird,  which  pecks  a  hole  in  the  shell  and 
comes  out  into  the  world.  The  condition,  however,  of 
the  young  birds  when  hatched  varies  greatly  in  different 
kinds.  Some,  like  the  young  thrushes,  are  naked,  help- 
less little  objects,  which  must  be  fed  by  the  parents  for 
a  long  time  while  their  feathers  are  growing  ;  while  others 
are  like  the  newly  hatched  chick  of  the  poultry  yard, 
a  dainty  little  creature  clothed  in  soft  down,  which  will 
catch  a  fly  for  itself  with  the  egg-shell  still  on  its  tail. 

England  is  very  specially  a  land  of  birds.  In  no 
other  European  country,  perhaps,  are  they  so  continually 
in  sight,  forming  a  constant  feature  of  every  country 
walk,  and  not  infrequent  in  towns  also.  Travellers  on 
the  Continent  must  have  noticed  the  comparative  scarcity 
of  birds,  which  have  to  be  searched  for,  instead  of  present- 
ing themselves,  as  here,  familiarly  at  every  turn. 

Birds  of  Prey. — The  first  Order  is  that  of  the  Birds 
of  Prey.  They  all  have  strong,  hooked  bills,  and  most  of 
them  sharp  powerful  claws  or  talons,  and  they  feed  on 
other  birds  and  animals,  either  hunting  and  killing  for 
themselves,  or  acting  as  scavengers  and  clearing  away 
what  they  find  dead  or  dying. 

The,  Falcons  and  the  Owls  are  typical  birds  of  the  two 


THE  FALCON  GROUP. 


95 


main  groups.  The  Falcon  group  includes  Vultures, 
Eagles,  Condors,  Hawks,  and  Kites ;  the  Osprey,  or  Fish- 
ing Eagle,  holding  an  intermediate  place  between  them 


Condor. 


and  the  Owl  group.  Owls  have  soft,  fluffy  feathers,  which 
enable  them  to  fly  very  silently,  large  heads,  little  or  no 
necks,  round  flat  faces,  with  eyes  looking  straight  forwards, 


ANIMAL   AND    VEGETABLE  KINGDOMS. 


instead  of  being  set  on  the  sides  of  the  head,  like  those 
of  other  birds,  and  a  general  air  of  composed  gravity. 
Falcons  always  have  three  toes  turning  forward  and  one 

at  the  back  of  the 
leg  ;  but  Owls  can 
turn  the  outermost 
of  their  front  toes 
either  back  or  for- 
ward as  they  please. 
The  poor  Owl  is 
often  unmercifully 
persecuted  by  game- 
keepers in  the  belief 
that  it  destroys  young 
pheasants  ;  but,  in 
truth,  it  is  often  ac- 
cused of  the  crimes 
committed  by  rats, 
while  it  really  does 

excellent  service  by  destroying  large  numbers  of  rats  and 
mice.  Indeed,  as  the  Owls  hunt  only  at  night,  it  is 
difficult  to  see  how  they  could  get  at  the  young  birds, 
which  are  then  safely  sheltered. 

Like  all  birds  of  prey,  Owls  throw  up  in  the  shape  of 
pellets  the  indigestible  parts  of  the  food  they  swallow, 
and  an  examination  of  706  pellets  found  about  a  Barn 
Owl's  nest  proved  them  to  contain  the  remains  of  16 
bats,  3  rats,  237  mice,  693  voles,  1590  shrews,  and  22 
birds. 

Picarian  Birds.  —  The  second  Order  takes  its  name 
of  Picarian  birds  from  the  Latin  name  of  Woodpecker 


CLIMBING  BIRDS. 


97 


(Picas),  which  is  considered  the  leading  type.  They  are 
generally  bad  nest-builders,  and  many  of  them  breed  in 
holes.  In  this  Order  there  are  many  groups.  Some  are 
Climbers  which  have  two  toes  turned  forward  and  two 
back,  an  arrangement  with  which  we  are  familiar  in  the 
Parrots.  These  beautiful  but  noisy  creatures,  of  which 
there  are  many  kinds,  are  found  only  in  the  tropics  and  in 


Woodpecker. 

Australia  and  New  Zealand.  The  last-named  country  is 
favoured  with  several  remarkable  and  troublesome  parrots 
of  its  own.  Parrots  have  strong,  large,  curved  bills,  with 
which  they  help  themselves  in  climbing  about,  and  the 
upper  side  is  jointed  so  that  it  can  be  lifted  right  up 
instead  of  being  faxed  to  the  bones  of  the  head  like  that 
of  most  birds.  Their  mouths  and  tongues  are  singularly 

H 


98        ANIMAL   AND    VEGETABLE  KINGDOMS. 

dry— indeed,  a  parrot  is  a  dry,  powdery  bird  altogether 
— and  they  are  continually  using  their  voices  screaming, 
chattering,  mimicking,  with  observant  accuracy,  and  a 
good  memory  which  has  been  turned  to  account  in 
teaching  them  to  talk.  It  is  very  difficult  to  believe 
that  a  parrot  is  entirely  unaware  of  the  meaning  of  its 
remarks,  they  are  often  so  quaintly  appropriate  and 
humourous.  Every  one  has  heard  good  stories  of  their 
conversation ;  but  few  are  better  than  that  of  the  parrot 
who,  having  once  or  twice  interrupted  the  reader  during 
family  prayers,  was  sent  out  of  the  room,  when,  as  he 
was  carried  to  the  door,  he  turned,  and  said  humbly, 
"  Sorry  I  spoke." 

Among  Climbing  Birds  also,  we  may  reckon  the  foreign 
Families  of  Honey  Guides,  Plantain  Eaters,  Toucans, 
and  Barbets,  and  they  are  represented  in  England  by  the 
Woodpeckers,  who  climb  with  their  claws  and  stiff  tails 
while  tapping  the  wood  in  search  of  insects,  and  the 
Cuckoos  who  visit  us  in  spring  and  summer,  and  who 
make  no  nest  for  themselves,  leaving  their  eggs  about  in 
other  birds'  nests  to  be  hatched. 

The  Picarian  Birds  also  include  Kingfishers,  of  which 
there  are  many  more  foreign  than  English ;  Hornbills, 
Trogons,  with  gorgeous  plumage  and  long  tails,  Goat- 
suckers, and  others,  as  well  as  the  dainty  little  Humming- 
birds,  which  hover  over  the  flowers,  shining  in  exquisite 
colours,  the  smallest  of  them  having  a  body  hardly  larger 
than  a  Humble  Bee. 

Perching  Birds  is  the  name  given  to  the  third 
Order,  a  very  large  one,  including  all  the  songsters,  and, 
in  fact,  almost  all  our  small  birds.  Their  feet  have  three 


PERCHING  BIRDS. 


99 


toes  forward  and  one  behind,  all  well  developed  and  with 
claws.  First  among  them  stands  the  Crow  group,  in- 
cluding Crows,  Rooks,  Jays,  Magpies,  etc.  Handsome 
cousins  of  the  Crows  are  the  Birds  of  Paradise  from  New 
Guinea  and  the  neighbouring  islands.  The  body,  wings, 
and  tail  of  one  of  these  beautiful  creatures  are  of  a 
rich  brown,  the  top  of  the  head  and  neck  pale  gold,  the 


Bird  of  Paradise. 

throat  and  under  side  of  head  emerald  green,  while 
from  under  each  wing  springs  a  tuft  of  feathery  golden 
plumes  two  feet  long,  which  falling  backward  mingle 
with  the  long  wire-like  feathers  of  the  tail. 

Among  the  Thrushes  and  Warblers  are  found  our  best 
song-birds ;  the  Thrush,  Blackbird,  and  Nightingale.  The 
Nightingale  arrives  in  England  in  the  middle  of  April, 


100      ANIMAL  AND    VEGETABLE  KINGDOMS. 

and  for  some  weeks  until  the  young  are  hatched,  pours 
out  its  song  almost  all  day  and  night,  except  for  an 
hour  or  two  in  the  evening.  It  does  not  show  itself 
very  freely,  but  otherwise  is  not  a  shy  bird,  often  singing 
its  best  by  the  roadsides.  Nightingales  seem  to  answer 
each  other,  and  may  often  be  started  in  song  by  whistling 
or  singing  to  them.  The  little  Wrens  and  Tits  are 
members  of  the  same  Order. 

Another  group  is  formed  by  the  lively  Families  of  the 
Finches,  Swallows,  Wagtails,  etc.  From  the  time  that 
the  welcome  Swallows  arrive  in  spring  till  they  assemble 
together  before  winter  for  their  departure  to  warmer 
countries,  they  are  constantly  in  sight,  sweeping  through 
the  air  or  over  the  surface  of  water  in  search  of  insects, 
with  rapid  and  graceful  flight,  or  building  round  our 
houses  or  under  our  eaves  the  little  plastered  nests  to 
which  the  same  birds  faithfully  return  year  after  year. 

Then  come  the  Starlings  and  their  relations,  among 
whom  are  the  cheery  Larks;  and  the  last  group  of 
Perching  birds  is  entirely  foreign,  including  Bell-birds 
and  Ant-thrushes  from  America,  and  the  beautiful 
Australian  Lyre  bird,  which  carries  its  lyre-shaped  tail 
feathers  erect  like  a  Peacock. 

Game  Birds  and  Pigeons. — To  the  Order  of  the 
Game  birds  belong  those  which  are  most  valued  for  the 
table,  all  the  varied  inhabitants  of  our  poultry-yards,  as 
well  as  the  Peacocks,  Pheasants,  Partridges,  and  Grouse. 
They  all  have  small  heads  for  the  size  of  their  bodies, 
and  scaly  markings  on  their  feet,  and  they  do  not  pair 
with  a  single  mate,  but  herd  many  together.  The  young 
birds  are  active  and  independent  as  soon  as  they  are 


WADERS. 


IOI 


hatched,  and  on  this  account  the  Pigeons,  whose  young 
are  naked  and  helpless,  are  iejiarajte/f'firom  tb'isX-frder  in 
which  they  were  formerly  reckoned.  ,......••«•,••  /, 

Waders.— Waders  coiije.  nex£, ,  '^,'-  as:  'iKei*  •  name 
shows,  are  mostly  to  be  found  near  water ;  but  a  few 
land  birds  are  included  with  them  which  have  the  same 
character  of  long  bare  legs,  small  head,  and  generally 
long  narrow  beak.  They  are  shy  birds,  migrating 


Flamingoes. 

annually,  and  they  mostly  breed  in  cold  climates,  making 
their  nests  on  the  ground. 

Rails  and  Crakes,  Moorhens  and  Plovers,  belong  to 
this  group,  and  — though  some  naturalists  place  them  in  a 
separate  Order — we  will  mention  with  them  the  Herons, 
the  Storks — so  familiar  and  highly  respected  on  the 
European  Continent,  where  they  constantly  make  their 
nests  on  the  roofs  of  houses — and  the  Flamingoes. 

No  one  who  has  seen  them  can  ever  forget  the  look 


102       ANIMAL  AND    VEGETABLE  KINGDOMS. 

of  these  last,  standing,  generally  on  one  leg,  in  the 
shallows  {  of  Lake"  ,-Menzakh  in  Egypt.  Troops  and 
troops  of  Othem.  some  five  or,  six  feet  in  height,  looking 
like  ^  regiment^, of ;,  soldiers  in  their  scarlet  and  white 
plumage,  and  occasionally  bending  down  their  long 
necks  to  rake  the  mud  in  search  of  food.  They,  how- 
ever, have  webbed  feet,  like  ducks,  and  must  therefore 
be  considered  as  intermediate  between  the  Waders  and 
the  Water  Birds. 

Water  Birds. — The  Water  Birds,  who  all  have 
webbed  feet,  are,  by  some  writers,  reckoned  all  together ; 
by  others  divided  into  half  a  dozen  different  Orders. 

Swans  are  found  mostly  on  fresh  water,  ducks  and 
geese  on  both  fresh  and  salt;  but  the  gulls  and  their 


Albatross. 

allies  belong  to  the  sea,  and,  from  their  numbers  and 
variety,  form  a  great  feature  of  life  on  every  sea  coast 
in  the  world.  The  grandest  of  the  whole  number  is  the 
Albatross,  whose  magnificent  wings,  when  outstretched, 
cover  a  space  of  some  twelve  feet  from  point  to  point. 
In  the  southern  seas  they  will  follow  a  ship  for  many- 
days  together,  to  pick  up  anything  eatable  among  the 


BIRDS    WHICH  DO  XOT  FLY. 


103 


refuse  thrown  overboard,  when  their  unrivalled  powers 
of  flight,  as  they  sail  sometimes  for  an  hour  without  a 
flap  of  the  wings,  are  a  source  of  the  greatest  interest  to 
the  voyagers. 

In  strong  contrast  to  these  splendid  flyers  are  the 
Penguins,  queer  birds  on  the  islands  of  the  southern 
ocean,  whose  little 
wings,  quite  useless 
for  flight,  are  modified 
into  flappers,  some- 
thing like  those  of  a 
Seal.  When  very  hard 
pressed,  they  actually 
use  these  for  running 
on  all  fours,  like  a 
quadruped  ;  but  their 
usual  attitude  is  that 
of  sitting  upright  on 
their  tails,  if,  indeed, 
they  can  be  said  to 
have  tails,  and  each  / 
bird  even  hatches  her 

single  egg  in  this  position  by  keeping  it  close  between 
her  legs.  The  largest  species  is  three  feet  in  height, 
and  they  crowd  together  in  communities  of  many 
thousands,  feeding  in  the  sea. 

Wingless  Birds. — The  last  Order  of  birds  is  also 
without  the  power  of  flight,  but  the  immense  speed  at 
which  they  can  run  makes  up  for  this  defect.  The 
Ostrich  of  the  African  plains  is  the  largest  of  all  living 
birds,  standing  from  six  to  eight  feet  high,  with  a  long 


Pengi 


104      ANIMAL   AND    VEGETABLE  KINGDOMS. 

neck  and  long  legs,  and  a  considerable  likeness,  from  a 
little  distance,  to  its  neighbour,  the  Camel.  It  has  two 
front  toes,  and,  like  all  the  rest  of  the  Order,  no  hind 
toe  at  all.  Contrary  to  popular  belief,  Ostriches  are  very 


careful  of  their  eggs,  the  male  birds  taking  a  full  share 
of  the  work  of  hatching ;  but  they  have  a  curious  habit 
of  laying  additional  eggs  round  the  outside  of  the  nest 
— a  mere  hollow  in  the  sand — which  serve  for  food  for 
the  young  birds  when  first  hatched.  There  seems  to  be 


BIRDS'   NESTS. 


105 


no  doubt  that,  at  all  events  for  a  short  time,  an  ostrich 
can  keep  up  a  speed  of  fifty  miles  an  hour,  and  if 
pressed  in  a  long  chase,  will  double  many  times  to 
throw  off  the  hunters. 

The  birds  are  valued  for  their  beautiful  plumes,  and 
ostrich-farming  has  now  become  a  regular  industry  of 
South  Africa. 

Birds'  Nests. — We  cannot  leave  our  feathered  friends 
without  a  word  of  admiration  for  the  nests  which  they 


Tailor-bird  nest. 


prepare  with  such  wonderful  skill  before  the  time  of 
egg-laying  comes  on.  At  the  Natural  History  Museum 
in  South  Kensington  you  will  find  a  large  and  beautiful 
collection  of  the  nests  of  different  birds,  forming  a 


106      ANIMAL  AND    VEGETABLE  KINGDOMS. 

delightful  and  instructive  study.  The  nest-building 
instinct  is  doubtless  a  habit  birds  have  acquired  for  the 
protection  of  their  young,  and  for  keeping  up  the  warmth 
necessary  for  the  hatching  of  their  eggs.  And  what  a 
wonderful  variety  of  nests  are  made  by  different  classes 
of  birds  !  The  Ostrich  merely  scrapes  a  hole  in  the 
sand ;  Sand-martins,  King-fishers,  etc.,  make  a  burrowed 
hole ;  Swallows,  Thrushes,  etc.,  make  a  well-built  nest  of 
mud  or  clay ;  Eagles  and  Storks  make  a  flat  nest  of  twigs 
on  elevated  spots ;  most  of  our  singing  birds  and  the  crows 
weave  a  nest  of  grass  or  hair  and  twigs ;  the  Bull-finches 
and  Humming  birds  make  a  soft  felt-work  nest  of  wool ; 
whilst  the  Wren,  Titmouse,  and  Water  Wagtails  build  a 
covered  nest,  with  an  entrance  on  one  side ;  a  few 
robbers,  like  the  Cuckoo,  and  the  Sparrow  if  he  gets  a 
chance,  use  the  nests  of  other  birds ;  on  the  other  hand, 
some,  like  the  Indian  Tailor-bird,  display  almost  human 
intelligence  in  the  construction  of  their  nests.  On  the 
last  page  is  a  picture  of  the  nest  of  the  so-called  Tailor- 
bird,  which  is  common  in  the  hedgerows  of  parts  of  India 
and  China ;  the  name  of  the  bird  is  derived  from  the  way 
it  prepares  its  nest.  Two  or  three  leaves  are  actually 
stitched  together  by  any  thread  or  fibre  the  bird  can  get, 
the  bird  using  its  bill  to  bore  the  holes  for  the  thread. 
A  sort  of  cradle  is  thus  formed  which  the  bird  lines  with 
cotton  wool  and  fine  grass  before  laying  its  eggs  in  its 
tailor-built  nest. 


CHAPTER   V. 

REPTILES    AND    AMPHIBIANS. 

WE  now  pass  to  the  Third  Class  of  the  Vertebrate 
Animals— the  Reptiles,  or  Creeping  Things.  Their 
blood  is  cold,  their  breathing  and  digestion  slow,  their 
eyes  cold  and  without  expression,  and  most  of  them  are 
rather  sluggish  in  movement.  They  show  wonderful 
tenacity  of  life,  many  of  them  being  able  to  endure  fasts 
for  months  and  even  years,  and  they  are  often  very 
hard  to  kill.  The  young  are  always  produced  from 
eggs,  even  though,  in  a  few  instances,  these  are  hatched 
before  leaving  the  mother.  Whether  it  is  from  the  un- 
pleasant, clammy  feel  of  these  creatures,  or  from  the 
deadly  powers  which  some  of  them  possess,  or  from 
causes  less  easily  assigned,  there  is  no  doubt  that  most 
people  feel  an  involuntary  repulsion  from  them.  They 
are  most  numerous  in  hot  countries,  diminishing  in 
number  as  we  go  north  and  south  from  tropical  regions ; 
in  England,  the  Class  is  represented  only  by  a  few 
lizards,  three  snakes,  and  some  frogs,  toads,  and  newts. 

Tortoises. — The  first  Order  is  that  of  the  Tortoises- 
creatures  with  four  limbs  and  without  teeth,  in  whom 
the  bony  skeleton,  instead  of  being  wholly  covered  by 
flesh,  comes  partly  to  the  outside  in  the  shape  of  large, 


108      ANIMAL   AND    VEGETABLE  KINGDOMS. 

bony  shields,  which  form  a  protecting  armour  over  the 
back  and  breast.  Some  of  the  Tortoises  are  able  to 
treat  their  shell  actually  as  a  house,  withdrawing  their 
heads  and  limbs  entirely  into  them ;  and  one  group,  the 
Box  Tortoises,  have  a  jointed  piece  of  shell  with  which 
they  can  close  their  doors  against  all  enemies,  but  others 
cannot  thus  protect  their  heads,  which  are  always  pro- 
truded from  the  shell.  They  all  lay  eggs,  digging  holes 
to  put  them  in  and  covering  them  over,  but  they  then 
leave  them  to  hatch  out  without  further  attention,  and 


do  not  watch  over  the  young,  who  are  lively  and  able 
to  take  care  of  themselves  as  soon  as  they  come  out. 
Many  sleep  all  through  the  winter,  burying  or  hiding 
themselves  under  rubbish,  and  all  become  more  sluggish 
when  it  is  cold.  There  are  sea  tortoises,  including  the 
green  Turtles,  so  much  valued  for  the  table,  freshwater, 
mud,  and  land  tortoises,  and  they  vary  in  size  from 
monsters,  five  and  a  half  feet  long,  four  feet  wide,  and 
three  feet  thick  in  the  body,  to  the  little  tortoise  from 
the  south  of  Europe,  which  is  often  imported  into 


CROCODILES  AND  ALLIGATORS.  IOQ 

England  as  a  garden  pet,  and  which  can  lie  on  a  man's 
hand. 

Crocodiles  and  Alligators  are  ferocious  reptiles, 
haunting  the  rivers  of  hot  countries.  Crocodiles  are 
found  in  Asia,  Africa,  Australia,  and  America ;  Alligators, 
which  differ  from  Crocodiles  in  their  bones  and  teeth,  in 
America  only,  except  one  kind  which  lives  in  a  river  in 
China.  They  have  flat,  long  bodies,  of  a  dirty,  dark 
colour,  protected  on  the  back  with  solid  scales,  and  long 
tails,  the  whole  length  sometimes  reaching  twenty  feet 


Crocodile. 

or  more.  Their  limbs  are  short  and  powerful,  and  their 
toes  somewhat  webbed,  and  they  can  go  either  in  the 
water  or  on  land,  but  are  much  more  nimble  in  the  water. 
Their  long  jaws,  armed  with  a  formidable  array  of  sharp 
teeth,  can  be  very  widely  opened,  and  as  they  will 
devour  anything  animal  that  comes  in  their  way,  they  are 
often  dangerous  enemies  to  men.  Considering  the  size 
of  the  full-grown  reptiles,  they  lay  strangely  small  eggs, 
not  larger  than  those  of  a  goose  ;  but  the  tiny  crocodiles 
that  emerge  from  them  are  very  like  their  parents,  and 
already  armed  with  their  sharp  teeth. 


IIO      ANIMAL  AND    VEGETABLE  KINGDOMS. 


Lizards.— In  the  Third  Order  of  Reptiles  we  find 
all  the  many  varieties  of  Lizards,  of  which  our  common 
little  English  lizard  may  be  considered  a  good  repre- 
sentative. It  is  about  six  inches  long,  with  a  slender, 
scaly  body  and  long  tail,  a  long,  forked  tongue,  and  fair- 
sized  limbs,  with  five  widely  spreading  toes.  In  warm 
weather  it  loves  to  lie  basking  in  the  sun,  or  darts  about 
in  a  lively  manner  catching  flies.  It  is  one  of  those 
whose  young  are  born  alive. 

All  the  Lizards  are  rather  apt,  when  handled,  to  snap 


off  their  tails,  which,  however,  grow  again,  a  peculiarity 
which  marks  them  as  animals  of  a  low  order.  They 
usually  have  four  limbs,  but  in  some  cases,  as,  for 
instance,  in  the  slow-worm,  no  limbs  are  visible  outside, 
only  traces  of  them  being  found  under  the  skin.  This 
makes  them  look  very  like  snakes,  from  which,  however, 
they  are  distinguished  by  the  shape  of  the  head  and 
manner  of  opening  the  jaws. 

There  are  Lizards  of  all  sizes,  the  Nile  Monitor,  which 
is  the  largest,  measuring  six  feet  in  length.     Some  live 


SNAA'ES.  I  I  I 

in  water,  some  on  land ;  some  have  long  forked  tongues, 
some  thick  fleshy  ones  just  notched  at  the  tip ;  several 
change  their  colour  under  different  circumstances,  of 
which  the  Chameleon  is  the  most  noted  example ;  and 
some,  like  the  Gecko,  have  flattened  feet,  like  suckers, 
which  enable  them  to  run  on  upright  and  slippery 
surfaces. 

Snakes,  the  most  formidable  Order  of  Reptiles,  are 
not  conspicuous  in  this  country,  but  in  some  hot  climates 


they  constitute  a  serious  danger.  The  outward  form  of 
a  Snake  is  well  known,  elongated  and  slender,  covered 
with  scales  and  without  limbs,  travelling,  often  with  great 
rapidity,  by  a  sort  of  gliding  movement,  extended  along 
the  ground,  but  able  to  lift  up  the  head  and  fore-part  of 
the  body.  But  the  speciality  of  Snakes  is  in  the  poison 
fangs  possessed  by  many  of  them. 

These  are  like  two  long  teeth  in  the  upper  jaw,  curved 
and  pointed  downward  when  extended  to  strike.  They 
contain  hollow  tubes,  and  when  a  wound  is  made  by  their 
sharp  points,  a  drop  of  colourless  venom  is  squeezed 


112      ANIMAL  AND    VEGETABLE  KINGDOMS. 

through  them  from  the  poison  bag  which  lies  behind  their 
base.  The  power  of  this  venom  varies  in  different  species ; 
thus,  the  bite  of  the  Viper,  the  only  venomous  Snake 

in  England,  though  it 
kills  small  animals,  is 
rarely  fatal  to  men, 
unless  they  are  already 
in  an  unhealthy  condi- 
tion; but  the  bite  of 

Head  of  Venomous  Serpent  showing  Fangs//.     ,        T     ...          _    .  . 

the  Indian  Cobra,  the 

African  Puff  Adder,  and  many  others,  will  kill  very  rapidly. 
A  Viper  may  always  be  known  by  the  zigzag  chain  of  dark 
markings  that  runs  down  the  spine,  while  our  common 
harmless  ringed  Snake  is  darkest  on  its  under  side  and 
of  a  lighter  greenish  grey  on  the  back.  Snakes  swallow 
their  prey  whole,  the  bones  of  their  jaws  being  loosely 
jointed  together,  and  so  far  separable  that  they,  as  well 
as  the  throat,  can  be  enormously  distended,  and  allow  of 
the  passage  of  objects  which  might  beforehand  be  thought 
far  too  large  to  go  down.  All  Snakes  are  not  venomous, 
but  some  of  the  Python  group,  which  have  no  poison 
fangs,  are  of  very  large  size,  sometimes  eighteen  or  twenty 
feet  long,  or  even  more,  and  they  kill  their  prey  by 
winding  their  coils  round  it  and  crushing  it  to  death. 
Even  animals  as  large  as  deer  are  swallowed  by  these 
serpents. 

Amphibia. — This  is  the  place  to  speak  of  the  Am- 
phibian animals,  which  have  been  sometimes  included 
under  Reptiles,  but  are  now  always  placed  in  a  separate 
Class.  Their  peculiarity  is  that,  when  hatched  out  of  the 
egg,  they  are  quite  unlike  their  parents,  and  only  by  a 


FROM  TADPOLE    TO  FROG. 


series  of  changes  gradually  acquire  the  same  form.  The 
best  known  of  them  are  Frogs  and  Toads,  which  are 
born  as  tadpoles,  little  dark  creatures  swimming  about 
in  water,  with  a  large  flat  tail  but  no  limbs,  and  the 
heart  and  breathing  apparatus  of  a  fish.  By  degrees  the 
limbs  begin  to  grow,  the  hind  legs  appearing  first  and 
then  the  front  ones ;  and  as  the  limbs  increase  in  size, 
the  tail  gradually  disappears,  not  dropping  off,  but  being 
absorbed  into  the  body. 

During  these  changes  the  little  creature  is  also  develop- 
ing lungs  fit  to  breathe  atmospheric  air,  and  as  soon  as 


and  Frog  in  different  Stages. 


the  tail  is  gone  it  comes  ashore  a  perfect  little  frog  or 
toad,  and  henceforward  spends  much  of  its  time  on  land, 
though  always  loving  moisture  and  haunting  cool,  damp 
places.  They  have  shiny  skins,  without  scales,  and 
remarkable  tongues,  which  are  fastened  to  the//w//  of 
the  lower  jaw,  and  lie  with  the  tip  pointing  down  the 
throat :  and  consequently  can  be  protruded  to  a  con- 
siderable distance  when  shot  out  in  pursuit  of  insects. 
Frogs  are  the  more  active  creatures,  moving  usually  on 
land  by  hops  and  leaps,  while  toads  crawl.  They  can 
be  tamed ;  and  toads  especially,  which  are  often  kept  in 


114      ANIMAL   AND    VEGETABLE  KINGDOMS. 

gardens  and  greenhouses  to  destroy  insects,  soon  come 
to  know  those  who  are  kind  to  them.  Toads  secrete  a 
kind  of  acrid  juice  in  their  skin,  which  makes  them  very 
distasteful  to  dogs  and  other  animals,  and  this  has  pro- 
bably given  rise  to  the  idea  that  they  are  venomous,  but 
they  have  no  real  venom. 

There  are  other  Amphibian  creatures  that  never  lose 
their  tails,  as  the  Salamanders  and  the  common  Newts, 
or  Efts  of  our  waters ;  and  a  word  must  be  said  of  an 
extraordinary  Mexican  Amphibian,  whose  eggs  hatch  out 
sometimes  what  we  may  call  the  tadpole  form,  but  some- 
times the  mature  form  at  once,  with  all  its  organs  com- 
plete. Moreover,  to  complicate  the  matter,  eggs  are 
laid  both  by  the  complete  creature  and  by  its  tadpole 
form,  and  there  is  no  telling  which  form  of  the  creature 
will  come  out  of  the  eggs  of  either.  The  immature 
animal  rejoices  in  the  name  of  Axolotl,  while  the  mature 
is  known  as  Amblystoma. 


CHAPTER  VI. 

FISHES. 

THE  last  Class  of  Vertebrate  creatures  is  that  of  the 
Fishes,  which  are  cold-blooded  and  live  entirely  in  water, 
breathing  through  gills  the  air  contained  in  the  water. 
A  fish  out  of  water  dies  when  the  gills  become  dry,  but 
two  or  three  species,  such  as  eels,  and  a  wonderful  fish 
called  the  Climbing  Perch,  have  gill  covers  able  to 


Skeleton  of  a  Fish  (Perch). 

retain  a  store  of  water  to  moisten  the  gills;  these  can 
maintain  life  out  of  water  as  long  as  the  store  lasts,  and 
are  thus  enabled  to  pass  from  one  pool  to  another. 

Most  fishes  are  covered  with  scales  overlapping  each 
other,  but  in  some  the  place  of  the  scales  is  taken  by 
bony  armour.  The  fins  of  a  fish  are  its  nearest  approach 
to  limbs,  and  the  two  front  pair  (pectoral  and  ventral), 


Il6      ANIMAL   AND    VEGETABLE  KINGDOMS. 

where  they  exist,  may  be  taken  to  represent  the  fore  and 
hind  limbs,  but  the  back  fins  (dorsal),  the  tail  fins  (caudal) 
and  the  anal  fin  (see  illustration),  have  nothing  that  corre- 
sponds to  them  in  the  higher  Vertebrate  animals. 

Fishes  are  produced  from  eggs  which,  like   those  of 
reptiles,  are  sometimes  hatched  before  birth,  and  their 


fertility  is  extraordinary,  the  number  of  eggs  which  form 
the  roe  of  a  single  fish  being  sometimes  counted  by 
millions.  The  eggs  and  young  are  generally  left  to  take 
care  of  themselves,  but  a  very  few  fishes,  among  whom 
are  some  of  the  Stickle-backs,  build  nests  and  watch  over 
their  young. 

If  we  take  the  Salmon  as  a  type  of  the  fish  form,  we 


may  notice  how  beautifully  it  is  built  for  rapid  motion, 
like  a  swift  ship,  its  sloping  lines  offering  the  least  possible 
resistance  to  the  water.  It  is  driven  forward  by  strokes 
of  the  tail,  the  fins  helping  to  balance  and  steady  the 


VARIOUS  FAMILIES  OF  FISH.  I  I/ 

body.  But  in  truth,  though  the  general  plan  of  fish 
shape  is  very  distinct,  there  are  really  endless  modifica- 
tions among  different  kinds.  Thus  there  are  fish  with 
their  mouths  at  the  end,  and  others  with  mouths  under- 


neath their  heads,  like  the  Shark  family,  the  larger 
members  of  which  are  the  terror  of  the  sea,  while  others 
again  have  long  snouts,  like  the  Pipe-fish,  or  formidable 
weapons  projecting  from  their  noses,  as  the  Sword-fish. 
The  great  Sunfish,  which  sometimes  reaches  a  length  of 


Il8       ANIMAL   AND    VEGETABLE  KINGDOMS. 

six  feet,  is  almost  round,  and  looks  rather  like  the  head 
and  shoulders  of  a  huge  fish  which  has  lost  the  rest  of 
the  body.  Skates  are  flattened  out  as  if  heavy  weights 
had  been  pressed  on  the  back  of  a  very  wide  fish,  and 
had  squeezed  it  into  a  sort  of  resemblance  to  a  child's 
kite :  and  on  the  other  hand  there  are  a  whole  group  of 
fishes,  squeezed  in  from  side  to  side,  which  are  in  the 
habit  of  lying  flat  on  the  bottom  of  the  sea,  and  so  have 


both  their  eyes  twisted  on  to  the  same  side  of  their  head, 
that  neither  of  them  may  be  underneath  as  they  lie. 
These  flat  fishes  are  very  excellent  food,  as  they  include 
the  Turbot,  Plaice,  Flounder,  Brill,  and  Sole.  But  the 
most  important  fisheries  are  those  of  the  Cod,  which 
are  found  most  plentifully  off  the  coasts  of  Newfound- 
land, and  of  the  Mackerel  and  Herring,  which  at  certain 
seasons  assemble  in  vast  shoals,  and  come  towards  the 


FRESH  AND  SALT-WATER  FISH.  1 19 

shores  for  the  purpose  of  spawning,  or  laying  their  eggs, 
followed  by  many  enemies  in  the  shape  of  birds,  large 
fish,  and  Cetaceans,  as  well  as  by  the  fishing-boats.  It 


is  a  pretty  and  interesting  sight  to  see  these  boats  come 
in  and  unlade  their  catch,  the  Mackerel  in  particular, 
being  a  beautiful  fish  coloured  dark  green,  black,  and 
silver.  Sprats  and  Anchovies  are  nearly  related  to  the 


Herring,  and  there  are  plenty  of  other  useful  sea-fish, 
while  the  fresh  waters  supply  Trout,  Carp,  Tench,  Barbel, 
Perch,  etc.,  and  there  are  both  fresh  and  salt-water  Eels. 
As  a  rule,  the  fresh  and  salt-water  fishes  keep  each  to 


I2O     ANIMAL  AND    VEGETABLE  KINGDOMS. 

their  own  domain ;  but  the  Salmon  migrate  annually 
between  them,  coming  up  the  rivers  to  lay  their  eggs, 
and  returning  to  the  sea  to  recruit  their  strength  after 
the  exhaustion  of  this  process.  It  is  considered  that  the 
migration  also  helps  to  free  them  from  parasites,  of  which 
the  river  kinds  are  killed  by  the  sea,  and  the  sea  kinds 
by  the  river  water. 


CHAPTER  VII. 

INVERTEBRATE   ANIMALS. 

IF  it  has  only  been  possible  to  give  a  very  slight  sketch 
of  the  main  Orders  of  the  Vertebrata,  what  can  be  said 
of  the  vast  families  of  the  Invertebrate  creatures,  of 


which  a  single  Order,  that  of  the  Beetles,  has  been 
estimated  to  contain  more  than  double  the  number  of 
species  of  all  the  Vertebrate  animals  put  together,  and 


122       ANIMAL   AND    VEGETABLE  KINGDOMS. 

in  which  the  individuals  are  simply  countless  myriads, 
apparently  becoming  the  more  numerous  the  smaller  their 
size? 

Mollusca. — Of  their  main  Divisions  the  first  is  that 
of  the  Mollusks,  creatures  with  soft  bodies,  either  naked,  or 
covered  in  whole  or  in  part  with  shelly  covering.  They 
have  a  mantle,  or  soft  membrane  surrounding  the  body, 
by  means  of  which  most  of  their  movements  are  made : 
and  the  higher  mollusks  have  a  kind  of  heart  and  blood 
vessels,  but  these  cannot  be  distinguished  in  the  lower. 

The  Octopus  and  Cuttle-fish  have  distinct  heads, 
round  which  are  set  long  tentacles  covered  with  suckers 
by  which  they  grasp  their  prey.  Some  of  these  creatures 
are  of  enormous  size,  well  authenticated  cases  being 
known  in  which  the  tentacles  or  arms  have  reached  forty 
feet  in  length.  Large  specimens  are  dangerous  enemies, 
for  whatever  they  grasp  they  hold  on  to  with  tremendous 
grip,  and  men  seized  by  them  have  only  escaped  by 
cutting  the  tentacles  to  pieces. 

Another  group  of  the  Mollusks  contains  snails,  slugs, 
and  the  shell-fish  that  form  what  are  called  univalve  shells, 
that  is,  shells  made  all  in  one  piece  like  a  snail-shell. 
These  are  often  extremely  beautiful  in  their  colouring 
and  marking,  and  very  various  in  shape,  but  they  almost 
all  have  a  tendency  to  be  spirally  coiled  up,  more  or 
less  tightly.  Some,  when  alive,  have  their  mantles 
wrapped  over  part  of  the  outside  of  their  shells,  but 
many  can  withdraw  themselves  entirely  into  their  shelter, 
like  the  snail,  who  only  puts  out  his  great  flat,  crawling 
foot,  and  his  head  with  its  eyes  carried  on  footstalks, 
when  he  is  satisfied  that  no  danger  is  near. 


CREATURES  INHABITING  SHELLS.  123 

Bivalve  shells,  which  form  another  group,  are  those 
made  in  two  pieces  and  hinged  together,  like  the  Oysters, 
Solens,  and  Scallops.  The  greater  number  of  their  in- 
habitants are  very  sedentary,  often  fixing  themselves  to 


Whelk.  Scallop. 

one  spot  for  their  whole  life.  Pearls  are  found  in  the 
shell  of  a  sort  of  oyster,  and  other  bivalve  shells  furnish 
the  beautiful  substance  mother  of  pearl. 


Arthropoda. — The  vast  Division  called  Arthropoda 
includes  all  that  have  jointed  legs  among  the  animals 
whose  bodies  are  arranged  in  successive  rings  or  seg- 
ments. They  may  be  divided  into  four  Classes. 

i.  The  Insects,  whose  bodies  are  in  three  parts,  head, 
thorax,  and  abdomen  :  they  always  have  six,  and  only 


124      ANIMAL   AND    VEGETABLE  KINGDOMS. 


six,  legs,  attached  to  the  thorax,  or  middle  division,  and 
two  antenna,  or  feelers  on  their  head;  and  generally 
one  or  two  pairs  of  wings  also. 

2.  The  Myriopoda,  or  many  legged  creatures,  Centi- 
pedes  and  Millipedes,  which  have  wormlike  bodies  in 


Caterpilla 


Pupa. 


Butterfly. 

successive  rings,  varying  in  number  from  ten  up  to  one 
hundred  and  sixty,  and  legs  on  nearly  every  segment. 

3.  Arachnida,  or  spider-like  animals,  with  eight  legs, 
and  no  wings  or  antennae. 


THE  LIFE  HISTORY  OF  AN  INSECT.         125 

4.  Crustaceans,  Crabs,  Lobsters,  etc.,  with  two  pairs 
of  antennae  and  many  pairs  of  legs.  In  some  the  body 
segments  are  very  distinct ;  in  others,  such  as  the  Crabs, 
some  of  them  are  welded  together  to  form  strong  shields 
on  the  back  and  breast. 

Insects  have  a  specially  interesting  life  history  in  the 
number  and  completeness  of  the  changes  which  many  of 
them  undergo,  being  hatched  from  the  egg  in  the  shape 
of  maggots,  grubs,  or  caterpillars,  which  can  only  crawl 
and  eat  voraciously  (this  is  called  the  larva  stage) ;  then 
passing  into  a  second  condition  called  the  pupa,  closed 
up  in  a  case  of  skin,  motionless  and  apparently  dead  for 
some  time,  until  the  case  at  last  splits  asunder,  and  the 
insect  comes  out  perfect,  and  generally  with  wings  where- 
with to  fly  about  in  the  air. 

Those  that  go  through  the  whole  of  these  changes  are 
the  Beetles,  whose  front  pair  of  wings  are  not  used  for 


Beetle  with  spread  wings. 

flying,  but  merely  form  horny  cases  or  sheaths  to  put 
away  the  flying  wings  in ;  the  Ants,  Bees,  and  Wasps, 
and  all  their  relations ;  the  Butterflies  and  Moths,  Caddis 


126      ANIMAL   AND    VEGETABLE  KINGDOMS. 


Flies  and  Lacewing  Flies,  all  the  innumerable  varieties 

of  two-winged  Flies,  and  the  Fleas. 

Volumes  have  been  written  about  the  Bees,  and  their 

wonderful  communities,  living  together  round  their  queen, 

, , ,    the  mother  of  the 

hive,  working  to- 
gether for  the 
common  good  at 
building  their 
beautiful  combs, 
collecting  honey 
from  the  flowers 
to  fill  them,  tend- 

Bee.  Ant. 

ing     the    young, 

and  when  the  hive  becomes  too  populous,  emigrating 
in  a  swarm  to  found  a  fresh  city  elsewhere.  Not  less 
wonderful  are  the  histories  of  Wasps,  and  of  the  Ants, 
some  of  whom  actually  keep  herds  of  the  tiny  Aphis, 
or  green  fly,  often  so  abundant  on  rose-trees,  and  do 
something  very  like  milking  them  regularly.  You  must 
read  about  them  in  larger  books. 

Butterflies  and  Moths,  the  loveliest  of  Insects,  have 
their  wings  clothed  with  tiny  feathery  scales,  which,  like 
works  of  inlaid  gems,  form  all  the  beautiful  colouring  and 
patterning.  The  scales  differ  in  shape,  and  are  beautiful 
objects  as  seen  through  a  microscope.  The  Butterflies 
have  long  antennas  ending  in  a  little  knob,  while  the 
antennas  of  Moths  are  pointed  at  the  tip,  though  often 
like  combs  or  feathers  below.  These  are  the  most 
conspicuous  and  interesting  insects  in  which  to  watch  the 
gradual  transformations  from  the  caterpillar  and  chrysalis. 


THE  FLY  GROUP. 


127 


To  the  Fly  group  belong  all  the  true  Flies,  the  Midges, 
Craneflies  or  Daddy-long-legs,  and  Gnats  and  Mosquitoes. 
These  last  lay  their  eggs  in 
water,  glueing  them  to- 
gether into  the  form  of 


perfect  little  boats,  which 
float  on  the  top  until  the 
eggs  hatch  out,  when  the 
larvae  fall  into  the  water, 
where  they  pass  their  early 
days. 

There   remain  some   in- 


Crane  Fly. 


sects  which  do  not  go  through  all  these  changes,  or  do 
so  only  imperfectly,  either  resembling  the  parents  from 
the  first,  or  being  active  in  the  pupa  stage.  Such  are 
the  Bugs,  including  Cicads,  Greenfly,  and  Froghoppers  ; 
the  Cricket  and  Grasshopper  group,  which  also  includes 


Grasshopper. 


Earwig,  flying. 


creatures  so  different  in  appearance  as  Cockroaches  and 
Earwigs,  White  Ants  or  Termites,  Mayflies,  Dragonflies, 
and  Springtails. 

The  second  Class  of  the  Arthropoda,  the  Centipedes 


128     ANIMAL    AND    VEGETABLE  KINGDOMS. 

(see  p.  14)  and  Millipedes,  show  very  distinctly  their 
formation  in  rings.  They  do  not  go  through  the  same 
series  of  changes  as  Insects;  but  in  some  Millipedes 
the  young  when  first  hatched  have  only  three  pairs  of 
legs,  acquiring  more  at  each  change  of  skin,  until  they 
fully  resemble  their  parents. 

The  third  Class,  which  includes  the  Scorpions  and 
Spiders,  have  eight  legs,  and  are  the  only  Arthropod 
creatures  without  antennae.  They  are  largely  car- 
nivorous, and  many  of  the  Spiders  make  nets  to  catch 
their  prey,  cleverly  spinning  their  thread  from  a  sticky 
substance,  which  issues  from  their  own  bodies.  They 
vary  in  size,  from  tiny  creatures  that  need  a  magnify- 
ing glass  to  distinguish  them,  up  to  monsters  whose 
legs  cover  a  space  of  six  inches,  and  who  are  able 
to  attack  and  kill  humming-birds  and  other  small  verte- 
brates. 

But  the  most  formidable  of  the  Arachnid  animals  are 
the  Scorpions,  found  in  most  hot  countries,  whose  terrible 


Scorpion. 

poisoned  sting,  though  rarely  fatal  to  the  life  of  a  man, 
"  puts  him,"  as  it  has  been  graphically  expressed,  "  to  the 
necessity  of  howling  for  the  next  four-and-twenty  hours." 


CRABS  AND  LOBSTERS.  129 

The  Order  of  Crustaceans  completes  the  number  of 
the  Arthropoda.  It  consists  of  Crabs  and  Lobsters, 
Prawns,  Shrimps,  "  Water-fleas,"  Barnacles,  and  such-like 
creatures,  mostly  covered  with  a  hard  shell  or  crust.  They 
almost  all  live  wholly  or  partly  in  water,  except  the 
familiar  Woodlice  which  haunt  our  gardens,  and  some 
Land-crabs.  These  Land  Crustaceans  resemble  their 
parents  from  the  time  they  come  out  of  the  egg;  but 
the  water  creatures  only  gradually  arrive  at  the  perfect 


form  through  a  series  of  changes,  much  more  gradual 
and  numerous  than  those  of  the  insects,  and  made 
through  successive  moultings  or  castings  of  the 
skin. 

Worms. — We  must  pass  on  to  a  few  words  about 
Worms,  an  extraordinarily  numerous  assemblage  of 
animals,  of  which  the  common  Earthworm  (see  p.  12)  is 
a  good  example,  so  useful  in  producing  good  soil,  and  so 
delightful  to  the  thrushes  and  blackbirds  that  busy  them- 
selves in  dragging  the  worms  from  their  holes.  They 
have  no  limbs  at  all ;  but  their  bodies  are  arranged  in  a 
series  of  rings  bearing  small  bristles,  by  means  of  which 

K  •»- 


130      ANIMAL   AND    VEGETABLE   KINGDOMS. 

they  move  with  a  sort  of  snake-like  motion.  Earthworms 
lay  eggs  ;  but  they  also  have  the  power,  if  cut  in  half,  of 
growing  a  fresh  head  or  tail,  so  that  the  one  individual 
becomes  two ;  and  in  several  of  the  Worm  Family  this 
power  goes  further,  and  they  divide  up  of  their  own 
accord,  the  tail  part  growing  a  fresh  head  before  it 
separates  from  the  old  one,  so  that  for  a  time  the  creature 
goes  about  with  two  heads  to  one  tail.  One  or  two 
species  carry  this  so  far  as  to  have  half  a  dozen  worms 
behind  them  sharing  their  tail,  all  of  which  eventually 
separate.  In  this  case  the  old  front  worm  alone  does  the 
eating,  while  the  supplementary  individuals  occupy  them- 
selves solely  in  laying  eggs. 

Some  of  the  sea  worms,  though  without  true  jointed 
limbs,  have  simple  projections  that  may  be  called  feet ; 
and  many  form  shelly  or  sandy  tubes  to  live  in.  A 
beautiful  example  of  the  tube  worms  is  seen  in  the 
Serpula,  well  known  to  any  one  who  has  studied  a  sea 
aquarium.  From  the  mouth  of  its  twisted  tube  it  pro- 
trudes a  plume  of  breathing  gills,  which,  when  fully 
expanded,  forms  a  brilliant  scarlet  fan,  beside  which 
stands  up  a  footstalk  carrying  a  stopper  of  the  same 
rich  colour.  But  the  Serpula  is  shy  :  at  the  slightest 
suspicion  of  danger,  sometimes  at  the  mere  falling  of  a 
shadow  across  the  water,  the  whole  pretty  show  is  gone 
like  a  flash  of  lightning,  withdrawn  into  the  shell,  the 
mouth  of  which  is  closed  with  the  scarlet  stopper. 

Besides  land  worms  and  water  worms,  there  is  a  highly 
disagreeable  set  of  parasitic  worms,  inhabiting  the  bodies 
of  living  animals,  where  they  often  give  rise  to  serious 
discomfort  and  disease.  Almost  all  creatures,  from  man 


TTtE  SERPULA. 


downwards,   are   liable   to   attacks   from    some   of   the 
numerous  species  of  Internal  Worms. 

The  three  Divisions  of  the  Invertebrate  Animals  thai 
remain  belong  entirely  to  the  water,  and  chiefly  to  the  sea. 


Serpula. 

Echinodermata. — First  come  the  creatures  the  parts 
of  whose  bodies  are  set  in  rays  round  a  central  opening, 
and  who  are  covered  with  prickles  or  spines.  If  any  one 
picks  up  and  handles  a  Starfish  (see  p.  14)  stranded  on 
the  seashore,  he  will  at  once  see  that  it  belongs  to  this 
group.  Starfishes  are  active  creatures,  walking  about  by 
means  of  the  innumerable  tiny  suckers  or  tentacles  with 
which  its  rays  are  furnished.  They  are  voracious,  and  do 
immense  damage  by  devouring  the  oysters  in  oyster  beds, 


132      ANIMAL   AND    VEGETABLE  KINGDOMS. 


and  often  take  the  bait  on  the  fisherman's  hook.  The 
angry  fishermen,  finding  that  their  catch  was  only  a 
worthless  starfish,  used  to  tear  them  in  half,  and  throw 
them  back  into  the  sea,  a  proceeding  which  made  two 
starfishes  in  the  place  of  one,  for,  like  most  creatures  in 
these  lowest  groups,  each  half  could  heal  its  wounds  and 
grow  again  what  it  had  lost ;  even  a 
single  arm  being  sufficient  to  grow  a 
new  starfish. 

They    lay    enormous    numbers    of 
eggs,  and  protect  the  young  until  they 
have  developed  their  rays  and  tentacles. 
To  the   same   Division  belong  the 
Sea-Urchins    or   Sea-Eggs,  the   upper 
part  of  whose  bodies  is  covered  with  a 
shell  of  most  elaborate  and  beautiful  construction,  armed 
all  over  with  spines;  and  also  the  Sea  Lilies  and  Sea 
Cucumbers. 

Coelenterata. — The  creatures  of  the  next  Division 


Jellyfish. 


are  distinguished  from  all  those  which  have  gone  before 
by  the  absence  of  a  body-cavity  between  the  body-wall 


JELLY-FISH  AND  SEA-ANEMONES.  133 

and  the  food-canal.  The  Jellyfish  are  like  beautiful, 
almost  transparent  umbrellas,  with  tentacles  hanging  down 
from  the  under  side,  and  they  float  in  the  water  with 
their  umbrellas  opening  and  partly  closing  in  a  constant 
pulsation.  They  vary  in  size  from  tiny  microscopic 
objects  to  a  diameter  of  several  feet,  and  many  of  them 
are  not  only  of  extreme  beauty  by  day,  but  shine  with 
phosphorescent  light  at  night.  There  are  few  more 
beautiful  and  interesting  sights  than  a  night  at  sea  when 
the  phosphorescence  is  strong ;  tiny  star  sparks  con- 
tinually snapping  in  and  out,  while  among  or  below 
them  float  the  pale  white  moons  of  the  larger  Jellyfish. 
Care  should  be  taken  by  sea  bathers  not  to  come  in 
contact  with  Jellyfish,  for  many  of 
them  sting  like  nettles,  and  a  few 
produce  really  severe  effects. 

The  pretty  Sea-anemones  are  fa- 
miliar to  all  dwellers  by  the  sea  side, 
and  a  great  ornament  to  the  aqua- 
rium ;  bearing  a  considerable  like- 
ness to  flowers  when  all  their  ten-  Sea-anemone 
tacles  are  spread  out,  but  when  these 
are  withdrawn,  subsiding  into  shapeless  lumps  of  jelly. 

Nearly  related  to  the  Sea-anemones  are  the  wonderful 
little  creatures  that  build  and  live  in  coral. 

Every  one  has  seen  coral,  dead  coral,  in  white 
branches  like  trees,  in  rounded  masses  folded  in  and 
out  like  the  brain,  in  clusters  like  multitudes  of  wee 
organ  pipes,  or  in  some  others  of  its  numerous  forms ; 
but  few  have  the  chance  of  watching  living  coral,  when 
every  little  tube  has  its  living  tenant,  and  they  thrust 


134      ANIMAL   AXD    VEGETABLE   KINGDOMS. 


out  through  every  pore  their  mouths  fringed  with 
tentacles  like  tiny  sea-anemones.  Corals  grow  on  the 
bottom  of  the  sea,  or  on  rocks  below  the  sea  level,  and 
increase  both  by  eggs  which  escape  from  their  mouths, 
and  by  budding  from  the  side  of  the  parent.  The 
little  creatures — polypes  they  are  called — deposit  hard 
structures  from  the  lime  contained  in  their  food  or 
absorbed  from  the  sea  water,  and  in  their  turn  bud  again. 
The  polypes  of  the  older  parts  die,  but  the  solid 
structure  remains  as  a  foundation  below  the  newer 


Coral.  Sponge. 

growth,  and  so  the  whole  mass  grows  until  reefs  of  great 
extent  are  formed,  generally  surrounding  islands.  The 
reef-building  corals  require  warm  seas,  and  they  are  prin- 
cipally found  fringing  the  islands  of  the  Indian,  Atlantic, 
and  Pacific  Oceans;  but  other  coral  polypes,  some  of 
which  dwell  separately  and  not  in  colonies,  belong  to 
cooler  seas,  and  some  are  found  on  our  own  coasts. 

We   may   conveniently   class   the    Sponges   with   the 
Zoophytes  and  Corals,  though  they  are  often  reckoned 


SIMPLEST  FORMS  OF  ANIMAL   LIFE. 


as  a  group  by  themselves.  The  simplest  form  of  sponge 
is  like  a  hollow  bag,  with  numerous  holes  through  which 
currents  of  water  pass  to  the  inside,  and  a  mouth  at  one 
end  through  which  the  water  passes  out.  As  the  water 
passes  through  the  sponge,  the  tiny  cells  which  line  the 
inside  feed  on  the  little  living  creatures  in  the  water. 
In  most  sponges  the  inside  lining  becomes  branched  into 
a  very  complicated  system  of  tubes  or  canals  leading  to 
chambers  where  the  feeding  goes  on.  A  hard  skeleton 
of  limy,  flinty  or  horny  spicules  or  fibres,  is  usually  de- 
veloped to  support  the  soft,  living  tissue  of  the  sponge. 

Protozoa. — Lastly  we  come  to  creatures  which 
throughout  their  life  are  simple  cells,  as  a  rule  so  tiny 
that  they  cannot  be 
seen  without  a  micro- 
scope, but  which  yet 
often  form  as  their 
dwelling  places  shells 
of  considerable  va- 
riety and  beauty ;  as, 
for  instance,  the  mi- 
nute sea- shells  which 
are  known  as  Fora- 
mi  nifera.  These 
shells  are  formed  of 
lime,  and  though  each 
of  them  is  not  bigger 
than  a  pin's  head,  yet 
their  accumulation  in 


Living  Foraminifer  (much  magnified). 


past  ages  has  formed  the   great  chalk   deposits  which 
we  all  know  in  the  cliffs  and  downs  of  the  south  coast  of 


136     ANIMAL   AND    VEGETABLE  KINGDOMS. 

England.  A  living  Foraminifer  collects  and  absorbs  its 
food,  and  is  able  to  move  about  by  means  of  ever- 
changing  and  interlacing  threads  of  living  matter  which 
stream  outwards  from  its  tiny  shell. 

As  an  example  of  a  simple  animal  belonging  to  the 
same  group  as  the  Foraniinifera,  but  without  a  shell,  we 
may  take  the  very  elementary  freshwater  creature  called 
Amceba,  consisting  of  a  single  cell  of  slimy  substance, 
soft,  naked,  constantly  changing  its  shape,  without  mouth 
or  stomach,  but  which,  nevertheless,  contrives  to  absorb 
other  living  creatures  by  putting  forth  processes  which 
surround  them,  and  gradually  digesting  them. 

We  have  now  passed  in  rapid  review  the  main  groups 
of  the  Animal  Kingdom,  from  Man  down  to  these 
simple  creatures  we  have  just  described,  which  remain 
all  their  lives  long  in  the  condition  of  single  cells.  It 
is  of  great  interest  to  remember  that  any  of  the  higher 
animals  begins  its  life  as  a  single  cell — the  egg-cell — 
from  which  it  is  built  up  by  a  slow  or  rapid  process 
of  growth.  So  it  is  believed  that  in  the  animal  world 
generally  there  is  progress  from  the  simple  to  the 
complex,  from  the  lower  to  the  higher  forms  of  life. 


(     137     ) 


CHAPTER  VIII. 

PHYSIOLOGY. 

AFTER  this  brief  review  of  animals  in  their  classes,  it 
will  be  interesting  to  examine  a  little  more  closely  how 
they  are  made,  what  are  the  different  parts  of  the  body, 
how  it  is  nourished  and  moved,  and  how  the  actions  of 
life  are  performed;  but  as  there  is  a  great  general  simi- 
larity in  construction,  wre  will  take  the  human  body,  the 
most  highly  developed  and  also  the  most  interesting, 
as  the  type,  and  while  giving  a  short  account  of  it,  will 
try  to  notice  at  the  same  time  some  of  the  main  points 
in  which  it  differs  from  other  animals,  or  in  which  they 
differ  from  one  another. 

The  pillars  and  foundations  of  the  body  are  to  be 
found  in  the  bony  skeleton,  which  supports  all  the  softer 
structures,  and  which  is  far  more  permanent  than  they, 
being  left  when  the  rest  of  the  body  decays. 

Look  at  the  picture  of  the  human  skeleton  on  p.  28,  and 
notice  first  the  main  central  pillar,  or  spine,  or  vertebral 
column,  reaching  from  the  central  part  of  the  body,  where 
the  legs  join  it,  up  to  the  skull.  It  is  formed  of  a  series 
of  small  similar  bones,  laid  one  on  the  top  of  the  other, 
and  jointed  together  by  a  tough  strong  substance,  so 
that,  though  quite  firm  and  strong,  it  is  not  stiff  like  a 


138      ANIMAL   AND    VEGETABLE  KINGDOMS. 

poker,  and  we  are  able  to  bend  it  a  little  when  we  stoop, 
or  lean  to  one  side.  The  skull,  which  rests  on  the  top 
of  it,  is  a  strong,  solid  bony  case,  hollow  inside,  with  the 
cavities  of  the  face  on  its  front  surface,  and  the  lower 
jaw,  which  is  a  separate  bone,  jointed  on  to  it. 

If  the  small  bones,  or  vertebrae  of  the  back,  are 
separately  examined,  it  is  seen  that  each  consists  of  a 
solid  central  portion  from  which  springs  a  bony  arch 
enclosing  a  hole  and  bearing  projections.  When  the 
vertebrae  are  laid  over  each  other,  the  holes  form  together 
a  continuous  tube  passing  right  up  the  centre  of  the 
column,  enclosed  in  a  strong  case  of  bone,  and  opening 
above  into  the  large  hollow  of  the  skull.  The  skull  and 
the  tube  together  are  like  a  strong  safe,  and  they  contain 
and  protect  a  most  important  treasure  which  we  shall 
speak  of  presently. 

The  jointed  backbone,  as  we  know,  is  the  distinguish- 
ing mark  of  all  the  Vertebrate  animals.  Look  at  the 
skeletons  of  creatures  from  different  Classes  of  the 
Vertebrata — on  pages  5,  7,  27,  28,  and  39 — and  you  will 
see  that  they  all  have  a  spine  and  a  skull,  but  both  the 
shape  and  number  of  the  vertebrae  differ  very  much 
in  different  creatures.  You  will  be  interested  to  notice 
some  of  these  varieties  on  the  dinner-table  in  the  animals 
we  use  for  food.  In  the  spine  of  a  pig  the  massive 
vertebrae  are  comparatively  simple  in  shape ;  but  the 
vertebra;  of  rabbits  are  complicated  with  sharp  pro- 
jections ;  so  are  those  of  a  fowl,  but  we  cannot  so  easily 
make  them  out,  as  all  the  winged  birds  have  their  hinder 
vertebrae  firmly  united  into  one  solid  mass. 

In  man  there  are  thirty-three  vertebrae,  and  they  come 


THE  JOINTED  BACKBONE. 


139 


to  an  end,  as  you  see,  just  below  the  attachment  of  the 
lower  limbs;  but  in  many  animals  they  are  continued 
into  long  tails  (see  p.  39),  and  some  large  snakes  have 
more  than  four  hun- 
dred,   moving    upon 
each   other  by  such 
free  joints   that   the 
creatures     can     coil 
themselves    up    into 
knots  (see  p.  5). 

The  seven  top 
joints  of  the  spine  in 
man  are  above  the 
attachment  of  the 
upper  limbs,  and  so 
belong  to  the  neck; 
and  it  is  a  curious 
thing  that  throughout 
all  the  Mammalia 
there  are  always  seven 
vertebrae  in  the  neck, 
neither  more  nor  less, 
except  in  those  odd 
creatures  the  Sloths, 
some  of  which  have 

nine  and  others  only  six.  Even  the  Giraffe  has  but 
seven,  and  consequently  each  bone  is  so  long  as  to 
make  his  long  neck  look  very  awkward  and  inflexible. 

With  birds,  on  the  contrary,  the  neck  vertebrae  vary  in 
number  from  nine  up  to  twenty-three,  so  that,  though  their 
backs  are  rigid,  their  necks  are  very  flexible  and  enable 


Skeleton  of  Fowl. 


140      ANIMAL  AND    VEGETABLE   KINGDOMS. 

them  to  reach  every  part  of  their  bodies  and  every 
feather  with  their  beaks. 

The  twelve  vertebrae  next  below  the  neck  (pages  27 
and  28)  carry  the  ribs,  long  curved  bones  bending  round 
to  the  front  of  the  body,  the  upper  part  of  which  they 
enclose  like  a  cage.  The  front  ends  of  the  ribs  do  not 
reach  right  to  the  flat  breast-bone,  and  the  two  lowest 
pair  are  very  short ;  but  most  of  them  are  joined  to  it 
by  bands  of  cartilage  or  gristle,  a  tough  strong  substance 
not  so  hard  as  bone.  All  the  Mammals  have  the  breast- 
bone, or  sternum,  as  it  is  called,  more  or  less  flat,  like 
that  of  a  man ;  but  in  the  flying  birds  it  is  large  and 
extended  forwards  into  a  sharp  ridge  or  keel,  as  is  well 
known  to  any  one  who  has  carved  the  breast  of  a  fowl 
(see  picture  on  last  page).  Coming  to  the  Reptiles, 
we  find  that  some  Lizards  and  Crocodiles  have  a 
sternum,  flat  like  those  of  the  Mammals ;  but  other 
Lizards,  Tortoises,  and  Snakes  dispense  with  it  entirely, 
as  do  also  the  Fishes. 

The  number  of  ribs  varies  greatly  in  different 
creatures. 

Next  we  come  to  the  limbs,  of  which  there  are  never 
more  than  two  pairs  in  Vertebrate  animals,  and  we  find 
that  each  pair  is  attached  to  and  supported  upon  a  sort 
of  bony  circle  or  girdle.  In  man  the  shoulder  girdle, 
which  extends  round  and  completely  outside  the  upper 
ribs,  consists  in  front  of  what  is  called  the  collar-bone, 
or  clavicle,  slightly  curved  strips  of  bone  joined  to  each 
side  of  the  top  of  the  sternum,  and  meeting  on  the  point 
of  the  shoulder  with  the  shoulder-blades,  large  flattened 
bones  which  form  the  back  of  the  circle. 


O  UR  BONY  FRAME  WORK.  \  4 1 

The  upper  part  of  the  arm  has  but  one  bone,  called 
the  humerus ;  but  from  the  elbow  to  the  wrist  we  find 
two,  so  jointed  to  the  elbow  that  the  arm  can  either  be 
bent  or  straightened,  and  so  attached  to  each  other  that 
the  arm  and  hand  can  be  turned  in  different  directions. 
Lay  your  hand  upon  the  table  with  the  palm  downwards, 
and  you  will  find  that  you  can  turn  the  palm  upwards 
without  moving  the  upper  arm  at  all,  by  the  rotating 
upon  each  other  of  these  two  bones,  of  which  that  widest 
at  the  elbow  is  called  the  ulna,  and  the  other,  which  is 
widest  at  the  wrist,  is  known  as  the  radius.  The  finger 
bones  are  called  digits,  and  their  separate  joints  phalanges. 

The  bony  girdle  which  supports  the  lower  limbs  and 
soft  lower  parts  of  the  trunk  is  called  the  pelvis.  In 
young  children  it  consists  of  three  bones  on  each  side, 
but  in  a  full  grown  person  the  three  are  firmly  grown 
together,  and  the  pelvic  bones  form  a  flattened  irregular 
sort  of  basin,  to  each  side  of  which  are  attached  the  leg 
bones.  The  bones  of  the  leg  correspond  to  those  of  the 
arm,  the  single  strong  bone  of  the  thigh  bearing  the  name 
of  femur,  the  two  between  knee  and  ankle  being  called 
the  tibia  and  fibula,  and  the  toes  sharing  with  the  fingers 
the  names  of  digits  and  phalanges. 

Now,  let  us  compare  the  bony  girdles  and  the  limbs 
in  other  animals.  Their  general  correspondence  with 
those  of  man  is  very  evident  on  looking  at  the  skeletons, 
and  we  can  generally  without  difficulty  name  each  bone 
from  those  of  the  human  skeleton.  It  is  true  that  Whales 
and  Manatees  have  no  hind  limbs,  and  Snakes  no  shoulder 
girdle  or  fore  limbs,  yet  we  find  in  all  these  Orders  very 
small  pelvic  bones,  not  joined  with  the  spine,  but 


142      ANIMAL  AND    VEGETABLE  KINGDOMS. 

embedded  in  the  flesh,  and  a  few  of  the  Snakes  have 
traces  of  actual  hind  limbs. 

A  principal  variation  from  the  human  type  is  in  the 
presence  or  absence  of  the  collar  bones  or  clavicles. 
It  seems  as  if  these  bones,  which  have  nothing  corre- 
sponding to  them  in  the  hinder  bony  circle,  were  only 
necessary  in  those  animals  which  use  their  forepaws  for 
something  else  than  just  to  stand  upon.  Bats  have  it 
well  developed  to  support  their  wings;  but,  as  the 
twisting  arrangement  of  the  fore  arm  might  make  their 
flight  unsteady,  they  have  the  ulna  reduced  to  very 
small  proportions,  while  the  fingers  are  enormously 
lengthened  to  carry  the  wing  membranes.  Rodents, 
also,  several  of  whom,  like  the  squirrels,  hold  up  their 
food  in  their  paws,  have  good  collar  bones,  and  so 
have  Sloths,  which  swing  by  their  long  arms  on  the 
tree  boughs,  and  Kangaroos,  which  use  their  forepaws 
almost  like  arms. 

But,  in  the  beasts  of  prey,  the  clavicle  is  either  absent 
or  very  little  developed,  and  the  forelimbs  are  not 
directly  attached  to  the  bones  of  the  trunk,  but  are  held 
to  it  only  by  cartilages  and  soft  structures,  so  that  a  tiger 
alighting  from  a  leap  does  not  get  a  great  jar  through  all 
its  frame  from  the  fall,  as  we  should  do.  The  absence 
of  the  clavicles  is  one  of  the  distinctions  that  marks  off 
the  beasts  of  prey  from  the  Insect-eaters  (p.  34). 

Elephants,  cattle,  deer,  horses,  etc.,  which  do  not 
lift  their  forelegs  high,  are  not  only  without  collar 
bones,  but  the  double  bones  of  the  limbs  are  so  fixed 
together,  that  there  is  no  power  of  rotating  them,  while 
they  are  strong  and  steady  as  supports. 


GENERAL   PLAN  OF  VERTEBRATES.         143 

We  may  be  sure  that  birds,  which  depend  so  much 
on  their  wings,  must  have  good  clavicles ;  and,  perhaps, 
we  shall  recognize  them  better  under  the  familiar  name 
of  the  merrythought. 

Look  back  at  the  skeletons  of  the  gorilla  (p.  27),  the 
lion  (p.  39),  and  the  snake  (p.  5),  and  compare  them  with 
that  of  the  man  (p.  28).  The  gorilla  is  really  not  unlike 
a  man,  except  for  its  very  long  arms,  receding  skull,  and 
prominent  jaws. 

As  to  the  lion,  try  for  a  moment  to  imagine  the 
skeleton  set  upright  in  the  same  position  as  the  man's. 
You  will  notice  that  its  hind  legs  can  never  be  com- 
pletely straightened  into  the  same  line  as  the  backbone, 
and  its  fore  limbs  can  neither  be  lifted  up  towards  the 
head,  nor  dropped  down  by  its  sides,  but  must  always 
stick  straight  out  in  front.  No  other  creature  but  man 
can  really  stand  and  walk  upright ;  some  of  the  apes 
come  nearest  to  it,  but  they  cannot  truly  straighten 
their  knees,  and  always  want  to  pull  themselves  up  by 
their  arms.  The  lion's  skeleton  shows  well,  too,  how 
all  the  cats  walk  on  their  toes,  with  the  heel  lifted  from 
the  ground,  though  pussy  puts-  down  the  whole  of  her 
back  feet  when  sitting  up  in  her  dignified  manner. 

Certainly  the  snake  is  different  with  its  absence  of 
limbs,  for  it  is  just  a  long  series  of  vertebrae  and  ribs, 
with  a  head  and  a  tail. 

Thus  we  see  that  the  general  plan  of  bones, — skull, 
spine,  ribs,  breastbone,  and  two  pairs  of  limbs  with  a 
bony  girdle  supporting  each, — is  traceable  on  the  whole, 
in  spite  of  variations  in  details,  throughout  the  Verte- 
brate animals.  The  widest  departure  from  it  is  in  the 


144      ANIMAL  AND   VEGETABLE  KINGDOMS. 

Fishes,  the  lowest  Class  of  Vertebra ta,  where  there  are 
additional  rows  of  small  bones. 

Let  us  pass  on  now  to  look  at  the  machinery  by 
means  of  which  the  bones  are  made  to  move  in  living 
bodies.  We  cannot  have  a  more  convenient  example 
to  begin  with  than  the  way  in  which  we  bend  and 
straighten  our  arms.  Here  is  a  figure  of  the  bones  of 


i.  Arm  hanging  down.  2.  Elbow  bent. 

Bones  of  Arm  with  biceps  muscle. 

the  arm  as  we  saw  them  in  the  skeleton ;  but  now 
there  is  added  a  certain  mass  of  flesh,  wide  in  the 
middle,  but  narrowing  down  at  each  end  into  firmer 
and  stronger  cords  called  tendons,  by  which  it  is 
fastened  to  the  bones.  The  lower  tendon  is  attached 
to  the  radius  of  the  arm  just  below  the  elbow,  while, 
at  the  upper  end,  not  one,  but  two  tendons  pass 


MUSCLE.  145 

upwards,  and  are  secured  round  the  shoulder  blade,  on 
to  which  the  arm  bone  is  jointed. 

Now  this  fleshy  mass,  which  is  called  a  muscle,  has 
the  power  of  contracting  in  length,  or  drawing  up  its 
particles  so  that  it  becomes  shorter  and  wider,  and 
when  it  does  this  it  draws  up  the  lower  part  of  the 
arm,  bending  it  upon  the  elbow  and  bringing  the  hand 
up  towards  the  shoulder,  in  the  position  shown  by  the 
outlined  arm  in  the  figure.  Stretch  your  arm  out  quite 
straight,  clasping  it  round  with  the  other  hand  about 
halfway  between  the  elbow  and  the  shoulder,  and 
then,  if  you  bend  the  elbow,  you  can  feel  the  muscle 
rising  up  under  your  hand  as  it  grows  thicker  and 
shorter. 

This  particular  muscle  is  called  the  biceps,  or  two- 
headed  muscle,  from  the  two  tendons  in  which  it  ends 
above,  and  its  work  is  to  bend  the  arm  ;  but  it  is  by 
no  means  the  only  one  in  the  arm.  There  is  another 
muscle  over  the  back  of  our  elbows,  and  when  this 
back  muscle  contracts  it  draws  the  lower  part  of  the 
arm  down,  and  so  straightens  it  out  again.  When  the 
arm  is  held  in  a  half-bent  position,  each  muscle  is 
partly  contracted,  and  the  pull  of  each  just  balances  the 
other. 

Muscle  is  what  we  know  as  "  lean  "  meat  or  flesh, 
and,  as  you  know,  the  bones  of  almost  every  part  of  the 
body  are  covered  with  this  soft  muscle.  It  does  not, 
however,  lie  anyhow,  like  mere  padding,  but  every  bit 
of  it  is  a  separate  muscle  which  has  its  own  definite 
direction  in  which  it  contracts,  and  its  own  proper 
fastenings  to  the  bones  or  other  parts  which  it  moves 

L 


146      ANIMAL   AND    VEGETABLE  KINGDOMS. 

by  contracting.  In  a  figure  of  the  human  body,  which 
has  the  skin  removed  so  as  to  show  the  flesh,  or  muscle, 
we  can  see  the  directions  in  which  some  of  the  muscles 
lie  and  in  which  they  must  contract.  In  the  same  way 
when  we  look  at  a  piece  of  meat  we  see  that  there  is 
a  distinct  grain  or  direction  in  which  the  bundles  of  fibres 
are  laid,  so  that  it  can  be  cut  either  with  the  grain  or 
across  the  grain  ;  and  the  fibres  lie  the  lengthway  of  the 
muscle. 

Many  muscular  contractions  often  go  to  the  perform- 
ance of  what  we  call  one  movement,  and  we  generally 
have  very  little  idea  of  how  the  obedient  muscles  carry 
out  the  orders  we  give  them  to  do  this  or  that.  So  when 
we  stand  upright  many  strong  muscles  are  at  work,  their 
contractions  being  balanced  against  each  other  to  keep 
us  in  this  position.  One  stretching  over  the  front  of 
the  knee  contracts  to  keep  the  knee  from  bending ;  the 
muscles  of  the  calf,  the  back  of  the  thigh,  and  up  the 
spine  are  contracting  sufficiently  to  prevent  us  from 
falling  forwards,  and  those  up  the  front  of  the  body  are 
at  work  to  keep  us  from  falling  backwards.  If  the  muscle 
of  the  back  of  the  neck  left  off  working  the  head  would 
sink  upon  the  breast,  or  if  the  front  muscles  of  the  throat 
failed  to  contract  it  would  fall  helplessly  backward ;  and 
we  can  see  that  this  is  just  what  happens  in  a  swoon, 
when  the  usual  work  is  not  going  on. 

When  a  muscle  is  at  rest  it  is  at  full  length;  all  its 
work,  its  labour,  its  effort,  is  in  shortening,  and  this 
labour  may  be  either  voluntary,  as  when  we  move  our 
arms  and  legs  on  purpose,  or  involuntary,  like  the  motions 
of  our  heart  and  our  chest  during  breathing,  which  go  on 


THE  IXSIDE   OF  THE  BODY,  147 

regularly  from  our  birth  till  we  die,  without  our  ever 
having  to  think  at  all  about  them. 

While  we  were  speaking  of  bones,  we  compared  the 
human  body  only  with  those  of  the  Vertebrate  animals, 
as  they  alone  have  bones,  but  now  the  whole  animal 
kingdom  can  come  into  comparison,  for  vigorous  muscles 
are  at  work  when  a  grasshopper  leaps  or  a  serpula  spreads 
its  tentacles,  as  well  as  in  a  tiger  striking  its  prey,  or  a 
swallow  migrating  across  the  sea.  The  breast  muscles 
of  flying  birds,  by  which  they  move  their  wings,  are  very 
largely  developed,  and  this  is  the  reason  why  the  breast- 
bone of  a  bird  should  be,  as  it  is,  extended  forward  in 
a  sharp  keel,  since  it  gives  far  more  space  for  the  attach- 
ment of  the  large  breast  muscles  than  it  would  if  it  were 
flat  like  those  of  mammals. 

Another  remarkable  development  of  muscular  power 
may  be  noticed  in  the  whale,  whose  vast  masses  of  flesh 
end  in  long  tendons,  which  run  just  like  rudder-cords 
down  to  the  tip  of  the  tail,  and  by  their  contractions 
turn  it  hither  and  thither  for  swimming  and  for  guiding 
the  body. 

This  body  of  ours,  supported  by  bones  and  overlaid 
with  muscles,  is  hollow,  and  we  want  next  to  know  what 
it  contains.  Look  at  this  general  picture  of  the  contents 
of  the  body  (see  next  page),  and  notice  first  that  it  is 
divided  in  two  by  a  partition,  D,  rather  above  the  middle. 
The  partition,  which  is  called  the  diaphragm,  is  partly 
of  flesh,  partly  of  a  sort  of  skin  or  membrane,  and  is 
attached  by  its  edge  all  round  to  the  sides  of  the  body  ; 
but  as  it  is  not  tightly  stretched  the  centre  can  move 
up  and  down.  The  upper  chamber,  which  is  above  the 


148      ANIMAL   AND   VEGETABLE  KINGDOMS. 

diaphragm,  is  the  part  of  the  body  enclosed  by  the  bony 
cage  of  the  ribs  and  breast-bone,  and  it  contains  the 
heart  and  lungs.  You  can  see  the  heart  in  the  middle, 
just  over  the  diaphragm,  D,  lying  between  the  large 
spongy  masses  of  the  lungs,  which  fill  up  the  cavity  on 
each  side.  The  lower  chamber,  which  is  soft  in  front, 


Human  Thorax  and  Abdomen  laid  open. 

is  called  the  abdomen,  and  contains    the  stomach,  the 
bowels  or  intestines,  and  some  other  organs. 

The  heart  is  a  complicated  bag,  enclosed  in  a  double 
membrane,  and  completely  divided  inside  from  top  to 
bottom,  so  that  there  is  no  interior  communication  at 
all  between  the  two  sides  of  the  heart,  and  the  only  way 
in  which  anything  can  pass  from  one  side  to  the  other 
is  by  going  out  through  the  passages  which  lead  out  of 


IIOIV  THE  HEAKT  DOES  ITS   WORK'.         14$ 

one  side,  and  going  all  round  to  get  at  the  passages 
which  come  in  at  the  other — and  a  very  long  way  round 
it  is.  It  is  like  a  block  of  two  houses  under  one  roof, 
each  with  front  and  back  doors,  and  no  way  for  the 
neighbours  to  meet  except  by  going  out  at  the  front 
door  of  one  house  and  round  to  the  back  door  of  the 


Diagram  of  the  Circulation  through  the  Heart  (Dalton). 

other.  Each  division  is  further  divided  into  two  chambers, 
one  above,  and  one  below,  making  altogether  four  parts, 
of  which  the  two  upper  are  called  auricles,  and  the  two 
lower  ventricles.  The  walls  of  the  heart  itself  are  formed 
of  a  network  of  muscles,  so  that  when  the  muscles  con- 
tract, they  give  a  squeeze  to  the  heart,  squeezing  out  some 
of  the  blood  that  it  contains,  just  as  you  squeeze  out 


150      ANIMAL   AND    VEGETABLE  KINGDOMS. 

some  water  when  you  tighten  your  fingers  round  a  damp 
sponge.  The  whole  of  the  heart  does  not  contract  at 
the  same  moment,  but  the  auricles  first  get  a  squeeze, 
and  the  next  instant  the  ventricles  follow,  after  which 
there  is  a  moment's  rest  while  they  expand  again.  The 
blood  thus  squeezed  out  runs  round  all  the  passages,  and 
comes  back  into  the  other  side  of  the  heart,  from 
which  another  squeeze  sends  it  through  a  second  set  of 
passages,  not  the  same  as  before,  round  again  into  the 
first  side ;  and  so,  as  the  heart  goes  on,  every  second  or 
oftener,  regularly  contracting — beating,  as  we  call  it — all 
the  blood  continually  runs  round  and  round,  making  the 
double  journey  and  getting  back  to  its  starting  point  in 
about  half  a  minute. 

Let  us  follow  the  blood  on  this  journey.  Starting 
from  the  left  ventricle  we  find  that  the  passage  from  it 
is  a  large  tube  with  firm  muscular  walls,  called  an  artery, 
which  like  the  stem  of  a  tree  branches  and  branches 
again  and  again  into  ever  smaller  and  smaller  tubes, 
spreading  through  every  part  of  the  flesh  of  the  body. 
There  are  arterial  tubes  passing  into  the  head,  the  arms, 
the  legs,  the  different  organs  of  the  interior,  even  into 
the  walls  of  the  heart  itself  (not  into  its  cavities),  and 
constantly  dividing,  they  come  down  at  last  into  innumer- 
able very  tiny  branchlets  with  very  thin  walls,  which  are 
called  capillary  tubes.  These  capillary  tubes  are  literally 
everywhere ;  you  cannot  make  a  prick  in  any  spot  of  the 
body  without  fetching  blood  from  them— and  the  blood 
in  them  gives  the  red  colour  to  the  flesh.  Now  the 
blood,  as  it  travels  along  the  arteries,  brings  with  it  all 
the  supplies  needed  for  the  nourishment  and  growth  of 


VEINS  AND  ARTERIES.  l$l 

the  tissues  of  the  body,  and  through  the  very  thin  walls 
of  the  capillaries,  as  through  a  filter,  every  one  of  these 
tissues,  as  the  different  materials  of  the  body  are  called, 
draws  from  the  blood  the  particular  substances  it  needs ; 
the  bony  tissue  takes  what  it  wants  to  make  bone,  the 
muscular  tissue  the  supplies  for  muscle ;  the  cartilages, 
the  fat,  the  skin,  each  finds  what  it  needs;  and,  more- 
over, each  of  these  gives  back  into  the  blood  to  be 
carried  away  all  that  it  has  used  up  and  done  with, 
consisting  chiefly  of  water,  ammonia,  and  a  gas  called 
carbonic  acid. 

In  fact,  the  blood  is  like  a  merchant  everywhere  selling 
food  to  the  tissues,  and  buying  up  and  carting  away  their 
dust  and  rubbish.  It  does  not  itself  go  out  of  the 
capillaries,  but  travels  always  inside  the  vessels,  carrying 
on  these  transactions  through  the  walls,  as  the  huckster 
might  stay  always  in  his  van,  giving  out  and  taking  in 
goods  through  the  windows.  After  this  distribution  the 
capillaries  begin  to  flow  together  again,  as  little  rivulets 
flow  into  river  channels,  until  all  the  distributed  streams 
are  gathered  again  into  large  channels,  finally  discharging 
themselves  in  one  great  vessel  into  the  right  auricle  of 
the  heart.  As  the  vessels  carrying  blood  to  the  capil- 
laries were  called  arteries,  and  the  blood  in  them  arterial 
blood,  so  the  vessels  bringing  it  back  to  the  heart  are 
called  veins,  and  the  blood  in  them  venous  blood. 
Instead  of  being  rich  bright  red,  the  venous  blood, 
charged  with  carbonic  acid,  etc.,  is  of  a  much  darker 
red  colour,  and  the  veins  themselves  are  not  so  firm 
and  muscular  as  the  arteries ;  their  walls  are  flabby  and 
fall  together  when  empty.  The  next  contraction  of  the 


152      ANIMAL  AND   VEGETABLE  KINGDOMS. 

auricles  drives  the  venous  blood  forward  to  the  right 
ventricle,  and  when  the  ventricles  contract  in  their  turn 
it  is  again  squeezed  out  into  a  great  artery  called  the 
pulmonary  artery,  which,  dividing  up  as  before,  carries 
it  this  time  to  the  lungs,  where  it  spreads  out  again  into 
capillaries.  Through  the  walls  of  these  the  carbonic 
acid  and  some  of  the  water  are  filtered  out  into  the 
little  spongy  holes  of  the  lungs,  and  when  the  chest 
contracts  and  squeezes  the  lungs  the  air  is  forced  up  the 
windpipe  and  out  through  the  nose  and  mouth  into  the 
atmosphere.  As  the  chest  expands  again,  clean,  fresh  air 
is  drawn  into  the  lungs,  and  the  blood  seizes  upon  the 
particles  of  oxygen  gas  which  it  contains,  draws  them 
into  its  tubes,  and  carries  them  along,  purifying  and 
brightening  itself  with  them  all  the  way,  as  it  travels 
back  through  larger  and  larger  veins  till  it  is  discharged 
into  the  left  auricle  of  the  heart,  from  whence  it  is  squeezed 
into  the  left  ventricle,  ready  to  begin  its  course  all  over 
again. 

The  journey  is  always  made  in  the  same  direction, 
and  blood  can  never  flow  backwards  the  wrong  way,  as 
the  openings  of  the  heart  and  the  passages  of  the  veins 
are  protected  by  valves,  which  are  like  swing  doors,  only 
opening  one  way,  letting  everything  pass  freely  in  the 
right  direction,  but  shutting  tight  against  any  pressure 
from  the  wrong  side. 

The  lungs  are  not  the  only  filter  by  which  the  blood 
is  purified — they  drain  off  most  of  the  carbonic  acid 
and  a  good  deal  of  water ;  but  the  skin  is  also  at  work 
getting  rid  of  water  in  the  form  of  sweat,  and  the  rest 
of  the  water,  with  the  other  refuse  substances,  is  filtered 


A   DROP  OF  BLOOD. 


153 


through  the  kidneys  into  the  bladder  and  so  passed  out 
of  the  body. 

If  we  prick  our  finger,  so  as  to  draw  a  drop  of  blood, 
and  then  examine  the  blood  through  a  microscope,  we 
shall  find  that  in- 
stead of  being  all  a 
red  liquid,  it  is  really 
an  almost  colour- 
less liquid,  in  which 
numbers  of  tiny  red 
things,  like  specks  of 
red  jelly,  float  about 
and  give  it  its  colour. 
They  are  round  and 
rather  flat  in  shape, 
like  thick  pennies, 
and  as  the  blood 
cools  they  have  a  tendency  to  stick  together  in  rolls,  like 
a  roll  of  copper  coins.  These  are  called  the  red  corpuscles 
— tiny  things— three  thousand  of  which  would  lie  side  by 
side  in  an  inch.  Among  them  wander  some  white  cor- 
puscles, which  are  fewer  in  number  than  the  red,  larger, 
and  not  flat ;  they  might  rather  be  called  globular,  but 
these  wonderful  little  things  are  always  changing  their 
shape,  and,  in  fact,  have  a  great  likeness  to  the  Amoeba, 
which  we  read  of  as  the  last  and  simplest  of  the  animals. 
The  liquid  in  which  the  corpuscles  float  is  called  plasma, 
and  has  the  property,  when  taken  from  the  body,  of 
thickening  like  the  white  of  egg  when  boiled,  and  making 
what  is  called  a  clot. 

The  blood  of  all  the  Mammalia  contains  two  kinds  of 


Blood  Corpuscles.     Magnified  Blood. 


154      ANIMAL   AND   VEGETABLE  KINGDOMS. 


corpuscles,  like  that  of  man ;  Birds,  Reptiles,  Amphibia, 
and  Fishes  have  red  and  white  corpuscles  in  their  blood, 
but  the  red  ones  are  oval  in  shape,  not  circular  like  those 
of  Mammals.  Those  of  the  Invertebrate  animals  which 
have  true  blood  at  all,  have  only  white  corpuscles  in  it. 
The  corpuscles  vary  a  good  deal  in  size  in  different 

creatures,  and,  strange 
to  say,  they  are  largest 
in  the  Amphibia. 

The  whole  arrange- 
ment of  the  circula- 
tion of  blood  gets 
simpler  as  we  look 


The  Heart  of  a  Frog(A>a«<z  Esculcnic)  from  the 

front. — V,  ventricle  ;  Ad,  right  auricle  ;  As,  Heart  of  i  Fish 

left  auricle;    B,  bulbu   arteriosus,  dividing 
into  right  and  left  aortae.    (Ecker.) 

down  the  series  of  the  animals.  In  the  Reptiles  the 
two  sides  of  the  heart  are  not  completely  separated 
except  in  the  Crocodiles ;  and  Frogs  have  two  auricles 
but  only  one  ventricle  ;  Fishes,  whose  blood  is  aired 
through  the  gills  instead  of  through  lungs,  have  but  one 
auricle  and  one  ventricle.  Among  the  Invertebrates 
some  Mollusks  have  a  simple  form  of  heart  with  auricle 
and  ventricle.  In  Arthropods  and  some  worms  the 


THE  STOMACH. 


155 


heart  is  an  enlarged   portion  of  the  main  blood-vessel 
which  pulsates. 

How  is  the  blood  supplied  with  all  the  materials  which 
it  carries  to  the  tissues  of  the  body  ?  We  take  them  in 
daily  in  our  food,  and  the 
whole  use  and  object  of 
feeding  is  thus  to  supply 
the  blood.  When  we 
put  food  into  our  mouth, 
it  is,  or  should  be,  first 
chewed  by  the  teeth,  and 
softened  and  somewhat 
changed  by  the  saliva,  or 
moisture  of  the  mouth,  and  then  it  goes  down  the  throat 
by  a  tube  which  passes  through  the  diaphragm  and  into 
the  stomach.  It  does  not  fall  down  the  throat,  but  the 

^Esophagus  or  gullet. 


Stomach  of  a  Mai 


st  stomach :  Paunch 
rumen. 


4th  or  rennet  stomach. 

Compound  Stomach  of  a  Cow. 


muscular  rings  surrounding  the  tube  contract  in  regular 
succession,  pushing  the  food  before  them.  This  enables 
us  to  swallow  when  we  are  lying  down  ;  and,  of  course, 
horses  and  all  grazing  animals  have  to  swallow  upwards. 


156      ANIMAL  AND    VEGETABLE  KINGDOMS. 

The  stomach  is  a  sort  of  bag,  holding,  in  a  full  grown 
man,  about  two  or  three  pints,  and  supplying  a  juice 
called  gastric  juice,  which  dissolves  or  digests  the  softened 
food,  and  makes  it  into  a  kind  of  milky  fluid.  Rumi- 
nating animals  have  the  stomach  divided  into  several 
compartments,  and  the  one  into  which  the  food  comes 
first  returns  it,  as  you  will  remember,  into  the  mouth 
again,  for  chewing  the  cud.  When  it  is  swallowed  the 
second  time,  it  passes  at  once  into  the  third  and  thence 
to  the  fourth  stomach,  in  which  alone  is  found  the  gastric 
juice  for  dissolving  it  (see  picture  on  last  page). 

From  the  stomach  the  soft  pulpy  mass  goes  out  into 
the  intestines  or  bowels — a  very  long  tube  coiled  up  in 
many  irregular  coils,  and  filling  all  the  lower  part  of  the 
abdomen,  p.  148.  Here  other  juices  are  poured  in  to  act 
upon  the  food ;  the  wall  of  the  intestine  itself  supplies 
what  is  called  intestinal  juice ;  pancreatic  juice  is  furnished 
by  an  organ  called  the  pancreas,  and  the  liver  adds  the 
greenish  yellow  fluid  known  as  bile.  All  these  juices 
are  selected,  or,  as  we  say,  secreted,  by  the  different 
organs  out  of  the  materials  brought  by  the  blood,  and 
poured  either  directly  into  the  stomach  and  intestines,  or 
conveyed  there  through  tubes. 

All  the  substances  that  we  eat  for  food  can  be  arranged 
into  three  divisions:  (i)  flesh-forming  matter  (called 
proteid  matter) ;  or  (2)  fatty  and  oily  matter;  or  (3)  starchy 
and  sugary  matter,  which  is  furnished  by  the  bread  and 
vegetables  of  our  food ;  all  the  rest  is  either  water,  or 
mineral  substances,  such  as  salt.  Now,  of  these  three 
kinds,  the  flesh-forming  matter  is  dissolved  by  the 
gastric  juice,  the  starch  by  the  saliva  of  the  mouth  and 


FOOD    AND   ITS  DIGESTION.  157 

the  pancreatic  juice,  and  the  fat  is  dealt  with  by  the  bile 
and  pancreatic  juice;  so  that  all  the  goodness  of  the 
food  becomes  quite  liquid,  and  is  drawn  into  the  blood 
through  the  busy  capillaries  which  are  found  crowded  in  all 
the  walls  of  the  intestines.  The  great  length  and  many 
folds  of  these  give  time  and  opportunity  for  the  whole 
nourishment  to  be  thus  taken  into  the  blood,  leaving 
nothing  in  the  tube  but  the  indigestible  refuse,  or  what 
we  might  call  the  papers  and  packing-cases  in  which  the 
nourishment  was  packed  up  in  our  food,  together  with 
what  remains  of  the  dissolving  juices. 

The  whole  of  the  food  passage  from  the  mouth  down- 
ward, including  the  stomach,  is  called  the  alimentary 
canal,  and  its  muscular  rings,  contracting  one  after  another, 
keep  pushing  the  food  forwards,  until,  the  goodness 
being  all  extracted,  the  remaining  mass  is  finally  pushed 
out  of  the  body  through  the  bowels. 

We  must  now  turn  to  consider  by  what  means  all  these 
processes — the  muscular  movements,  the  circulation  of  the 
blood,  and  the  digestive  apparatus — are  regulated.  The 
connecting  and  controlling  organization  which  governs 
and  directs  and  keeps  everything  in  order  is  found  in  the 
nervous  system,  which  has  its  centre  in  the  brain. 

The  brain,  which  occupies  the  large  hollow  of  the  skull, 
consists  of  soft  grey  and  white  nerve  matter,  arranged  in 
definite  parts,  and  folds,  and  shapes.  The  same  nerve 
matter  is  continued  all  down  the  tube  in  the  vertebral 
column,  and  is  there  called  the  spinal  cord ;  and  both  the 
brain  and  the  spinal  cord  give  off  many  branches  or  nerves, 
which  spread,  like  the  blood-vessels,  into  every  part  of 


Diagram  showing  the  Human  Brain  and  the  Spinal  Cord. 


THE  NERVOUS  SYSTEM.  159 

the  body,  in  the  form  of  very  fine  white  threads.  The 
nerves  that  start  from  the  brain,  coming  through  little 
holes  in  its  bony  case,  chiefly  supply  the  head  and  face, 
while  the  spinal  nerves,  issuing  between  the  vertebrae  all 
down  the  back,  spread  their  branches  into  every  muscle, 
and  into  the  whole  surface  of  the  skin. 

Now,  these  fine  white  threads  act  the  part  of  telegraph 
or  telephone  wires.  Whatever  impressions  from  outside 
are  made  upon  the  body — of  injury  or  resistance,  heat 
or  cold,  scent,  sound,  or  light — are  instantly  telegraphed 
through  the  nerves  to  the  brain,  and  there  become  sensa- 
tions or  feelings.  The  brain  in  turn  telegraphs  orders 
through  nerves  to  the  muscles  when  they  are  to  contract, 
and  so  bring  about  various  movements.  The  nerves 
which  bring  information  to  the  brain  are  called  sensory 
nerves ;  they  end  chiefly  in  the  skin,  and  are  not  very 
evenly  distributed,  some  sensitive  parts,  like  the  tips  of  the 
fingers,  being  crowded  with  nerve  fibres,  while  the  back  of 
the  hand  has  comparatively  few.  Those  which  carry  orders 
from  the  brain  to  the  muscles  are  called  motor  nerves  ; 
they  end  in  the  muscles,  and  no  muscle  ever  contracts 
unless  it  receives  a  nerve  message  or  stimulus  to  do  so. 

It  does  not  at  all  follow  that  we  are  always  conscious 
of  the  nerve  orders  given  in  our  own  bodies,  or  that 
we  can  always  control  them.  The  nerves  bring  in  a 
message  that  the  skin  is  cold,  back  flashes  the  impulse  to 
shiver ;  the  nerves  of  the  eye  say  something  is  approach- 
ing or  touching  the  eye,  and  the  eye-lid  instantly  winks 
in  obedience  to  an  unconscious  command. 

Nay,  sometimes  we  would  give  anything  to  prevent 
the  action.  The  ear  nerves  report  words  that  are  heard ; 


I6O      ANIMAL  AND   VEGETABLE  KINGDOMS. 

why  should  the  muscles  controlling  the  blood-vessels  of 
the  face  and  neck  immediately  have  the  orders  for  their 
firm  contraction  revoked,  so  that  they  are  overfilled  with 
blood,  and  make  us  blush  scarlet?  We  even  try  to 
resist — endeavouring,  perhaps,  to  keep  cool  and  firm, 
when  something  has  ordered  our  heart  to  throb  and 
our  hand  to  shake. 

All  these  cases  of  movements  without  our  control, 
and  often  without  our  knowledge,  are  said  to  be  cases 
of  reflex  action,  as  if  messages  from  the  sensory  nerves 
were  simply  reflected  back  from  the  nervous  centres  to 
the  motor  nerves ;  and  it  is  remarkable  that  to  produce 
reflex  action,  it  is  not  always  necessary  that  the  message 
should  reach  the  brain  itself ;  for  not  only  can  the  spinal 
cord  issue  orders  to  the  muscles,  but  it  seems  that  this 
power  is  even  shared  to  some  extent  by  a  series  of  little 
masses  of  nerve  matter,  known  as  the  sympathetic  ganglia, 
which  lie  in  front  of  the  vertebral  column,  and  are  con- 
nected by  nervous  cords  with  each  other,  and  the  nerves 
of  the  brain  and  spine. 

The  seat,  however,  of  sensation,  and  of  all  the  mental 
powers,  intelligence,  reason,  thought,  is  in  the  brain 
or  cerebrum  only ;  and  it  alone  is  the  source  of  voluntary 
muscular  contraction. 

Why  the  nerve  messages  excite  feelings  in  the  brain, 
how  the  brain  is  used  in  reasoning  or  remembering,  or 
how  the  living  being  which  exercises  control  by  its 
means,  is  connected  with  it ;  to  these  questions  science 
has  no  answer  to  give.  The  mystery  of  life  is  above 
and  beyond  its  reach,  even  while  it  examines  into  the 
sources  of  sensation,  the  machinery  for  motion,  and  the 


SPECIAL    ORGANS  OF  THE  SENSES.          l6l 

carrying  out  of  the  orders  of  the  will.  That  the  nerve 
messages  are  carried  as  above  described  is  proved  by 
the  facts  that  when  certain  nerves  are  cut  or  injured, 
sensations  of  certain  kinds,  or  of  certain  parts  of  the 
body,  are  entirely  stopped,  while  injury  to  others  takes 
away  the  power  of  muscular  contraction  from  the  limbs 
to  which  these  nerves  extend ;  that  division  of  the  spinal 
cord  puts  an  end  both  to  feeling  and  motion  in  all  parts 
supplied  by  spinal  nerves  issuing  below  the  injury  ;  but 
that  thought  and  intelligence  are  not  affected  unless  the 
injury  is  in  the  brain  itself. 

A  few  words  must  be  said  about  the  special  organs 
of  the  senses.  We  fed  through  the  nerves  all  over  our 
body,  but  we  can  only  taste  and  smell  with  the  mouth 
and  nose,  hear  with  the  ears,  and  see  with  the  eyes. 
The  special  nerve  which  produces  the  sensation  of  smell 
has  its  delicate  branches  spread  over  the  inside  of  the 
nose,  while  its  trunk  ends  in  the  brain,  and  the  nerve 
of  taste  spreads  in  like  manner  over  the  back  of  the 
palate  or  roof  of  the  mouth  and  the  tongue,  and  before 
either  of  these  can  act  they  must  come  into  contact  with 
the  actual  particles  of  substance  which  are  tasted  or 
smelt.  But  light  and  sound  are  brought  to  us  imper- 
ceptibly, without  our  being  in  actual  contact  with  the 
luminous  or  resounding  substances,  so  that  the  eye  and 
ear  are  our  means  of  communication  with  other  men, 
and  with  the  outer  world,  while  to  the  eye  is  also  given 
the  wonderful  power  of  searching  the  unspeakable  dis- 
tances of  the  starry  sky. 

The  ear  is  hidden  deep  within  the  skull,  only  the 
outside  porch  being  visible.  It  consists  of  an  intricate 

M 


l62       ANIMAL  AND    VEGETABLE  KINGDOMS. 

labyrinth  of  chambers  and  winding  passages,  some  of 
which  are  filled  with  air,  and  some  with  liquid,  entirely 
closed  from  outside  by  fibrous  membranes.  One  of  the 
inner  chambers  carries  on  its  walls  a  set  of  marvellously 
fine  fibres,  like  microscopic  harp-strings,  each  of  which 
responds  to  a  different  pitch  of  sound;  and  when  any 
audible  vibrations  come  floating  on  the  air,  the  mem- 
branes, the  air,  and  the  liquids  of  the  ear-chambers  carry 
them  inwards  till  they  reach  and  strike  the  dainty  harp- 
strings,  which,  being  in  close  connection  with  the  ends 
of  the  auditory  nerve  or  nerve  of  hearing,  excite  it  to 
telegraph  its  message  of  sound  into  the  brain. 

Observe  also  the  power  of  the  ear  to  hear,  and  dis- 
tinguish many  sounds  at  once,  as  in  the  harmonies  of 
music.  "  Picture  to  yourselves  the  contrast  between  a 
great  orchestra  containing  some  hundred  performers  and 
instruments,  and  that  small  music-room  built  of  ivory, 
no  bigger  than  a  cherry  stone,  which  we  call  an  ear, 
where  there  is  ample  accommodation  for  all  of  them  to 
play  together.  The  players,  indeed,  and  their  instru- 
ments are  not  admitted,  but  what  of  that  if  their  music 
be  ?  Nay,  if  you  only  think  of  it,  what  we  call  a  musical 
performance  is,  after  all,  but  the  last  rehearsal.  The 
true  performance  is  within  the  ear's  music-room,  and 
each  one  of  us  has  the  whole  orchestra  to  himself."  * 

The  eye,  through  which  the  brain  receives  its  messages 
of  light  and  vision,  is  a  hollow  globe  of  tough  tissue  (the 
same  material  of  which  tendons  are  made),  to  whose 
outer  surface  are  attached  six  different  muscles  enabling 
the  eyeball  to  be  moved  up  and  down  or  from  side  to 
*  "  The  Five  Gateways  of  Knowledge."  George  Wilson. 


THE  EYE.  163 

side,  so  as  to  see  freely  round.  In  front  of  the  globe 
the  tissue  is  modified  into  a  clear  window,  something 
like  a  watch-glass,  called  the  cornea,  which  is  always 
kept  spotlessly  clean  by  the  winking  of  the  eyelids.  A 
little  way  behind  the  window  is  placed  the  elastic 
crystalline  lens,  or  magnifying  glass,  set  in  a  delicate 
membranous  frame,  whose  edges  reaching  to  the  walls 
of  the  eyeball,  divide  the  hollow  chamber  into  two  parts, 
both  of  which  are  filled  with  liquid;  and  close  in  front 


SECTION  OK  EYEBALL. 

t.  Cornea;  2.  Retina  ;  3.  Optic  nerve  ;  4.  Crystalline  lens;  =;.  Vitreous  humour  ; 
6.  bclerotic  coat ;  7.  Ins ;  8.  The  yellow  spot,  the  central  and  most  sensitive 
part  of  the  retina. 

of  the  lens,  between  it  and  the  cornea,  hangs  the  iris, 
a  coloured  curtain  with  a  circular  opening  which  enlarges 
or  contracts,  so  as  to  regulate  the  amount  of  light  passing 
into  the  eye.  On  looking  attentively  at  another  person's 
eye,  or  at  your  own  in  the  glass,  you  can  see  the  iris  as 
the  coloured  part,  in  the  centre  of  which  appears  what 
we  call  the  dark  pupil  of  the  eye,  which  is  really  part 
of  the  dark  hollow  seen  through  the  clear  crystalline 


1 64      ANIMAL  AND    VEGETABLE  KINGDOMS. 


lens.  When  the  light  is  very  bright,  the  hole  in  the 
iris  contracts,  and  the  pupil  appears  small ;  but  in  the 
dusk  it  enlarges  so  as  to  admit  more  light.  If  you  keep 
your  eyes  shut  for  a  few  minutes,  and  then  open  them 
suddenly  before  a  looking-glass,  you  can  see  the  pupil 
which  had  become  larger 
in  the  dark  rapidly  con- 
tracting as  the  light  falls 
upon  it. 

The  back  of  the  eye- 
ball is  lined  with  a  soft 
dark  curtain,  on  the  inner 
side  of  which  is  spread  a 
very  delicate  white  mem- 
brane called  the  retina, 
containing  the  fine 
branches  of  the  optic 
nerve,  or  nerve  of  seeing, 
whose  trunk  end  is  in  the 
brain. 

Turning  now  to  the 
animals,  we  find  that  the 
nervous  system  of  the 
Vertebrata  is  on  the  same 
pattern  as  that  of  man, 

Nervous  System  of  Frog. 

with   its    centre    in    the 

brain,  and  with  the  spinal  cord  giving  off  the  nerves 
which  spread  into  fine  branches  through  the  body.  Here, 
for  example,  is  a  picture  of  the  nervous  system  of  a 
frog.  The  intelligence  of  animals  seems  to  vary  partly 
with  the  size  of  the  brain,  and  partly  with  the  number  of 


THE  NERVES   OF  THE  IXVERTEBRATA.     165 

folds  in  it;  and  many  of  them,  as  we  know,  have  the 
special  senses  keenly  developed,  as,  for  instance,  the 
sight  in  birds  of  prey,  and  the  scent  in  dogs  or  ferrets. 

But  when  we  come  to  the  Invertebrate  creatures,  the 
highest  nervous  centres  consist  of  ganglia,  sometimes 
collected  together  into  larger  nervous  masses,  sometimes 
placed  singly,  one  in  each  segment  of  the  body,  and 
connected  by  nerve  cords,  as  is  shown  in  this  picture  of 


Nervous  System  of  Karthworm. 

the  nervous  system  of  the  common  earthworm.  Yet  in 
the  Insects,  for  instance,  such  a  large  and  important 
nerve-mass  is  present  in  the  head  that  it  is  often  called 
the  "  brain."  Still  lower  in  the  scale,  as  in  the  starfishes, 
even  ganglia  disappear,  and  we  find  a  mere  ring  of  nerve 
round  the  mouth,  with  cords  radiating  from  it  into  the 
principal  divisions  of  the  animal. 

At   the   same   time   the    eyes,   which   in   insects    are 


1 66      ANIMAL   AND   VEGETABLE  KINGDOMS. 

elaborately  compound,  and  in  spiders  numerous,  become 
in  lower  forms  mere  sensitive  points,  perhaps  dimly 
conscious  of  light,  but  not  perceiving  shapes  or  colours ; 
until,  finally,  we  come  down  to  creatures  of  the  simplest 
organization,  without  perceptible  nerves,  circulation,  or 
even  stomach,  and  hardly  to  be  distinguished  from  the 
lower  forms  of  plant-life.  Indeed,  in  these  borderlands 
of  animal  and  vegetable  nature,  the  main  difference 
seems  to  be  that,  while  plants  can  take  in  and  digest 
inorganic  substances,  thus  converting  them  into  organized 
matter,  animals  can  only  sustain  life  upon  food  already 
organized  either  in  plants,  or  in  other  animals. 


1 6 


CHAPTER    IX. 


PLANTS  have,  for  our  present  purpose,  the  very  great 
advantage  over  animals  that  they  stand  still  to  be  looked 
at,  and,  as  they  are  to  be 
found  almost  everywhere, 
you  are  now  invited  to 
examine  and  see  their 
arrangements  for  your- 
selves, and  not  only  to 
read  about  them,  as  we 
are  often  obliged  to  do 
with  animals. 

First,  then,  let  us  go 
and  dig  up  a  Buttercup 
plant  by  the  roots,  the 
largest  we  can  find,  and, 
shaking  it  as  free  as  pos- 
sible from  earth,  lay  it  on 
the  table  to  look  at.  At 
the  bottom  come  the 
roots,  a  mass  of  fibres, 
which  were  all  buried  out  Buttercup  Plan.. 

of  sight  underground ;  above  these  shoots  up  the  strong 


1 68       AXIMAL  AXD    VEGETABLE  KINGDOMS. 

green  stem  with  many  branches,  carrying  a  number  of 
green  leaves,  and  at  the  top  are  the  large,  bright,  shining, 
yellow  flowers.  If  some  of  the  flowers  are  already  over, 
we  may  see  their  places  occupied  by  the  seed-vessels, 
which  were  inside  the  flowers,  and  which  contain  the 
seeds. 

Now,  if  we  look  at  an  Oak  tree  we  shall  find  that  it 


also  has  a  mass  of  roots  underground,  a  strong  stem 
shooting  up,  with  branches  carrying  many  green  leaves 
and  flowers,  within  which  are  the  seed-vessels  containing 
the  seeds.  And,  in  fact,  this  is  the  general  character  of 
all  flowering  plants,  though  there  are  many  variations  in 
details,  some  of  which  we  will  look  at. 


VARIOUS  KINDS   OF  ROOTS. 


I69 


We  shall  now  need  some  more  plants  for  comparison, 
and  had  better  dig  up  a  Daisy,  a  Plantain,  a  Dandelion, 
a  Potato,  a  Turnip,  a  Crocus,  if  we  can  find  one,  and  a 
Lily  of  the  Valley ;  but  these  two 
last  bloom  in  the  spring,  and  their 
flowers  will  be  over  when  the 
others  come  out.  Lay  them  in  a 
row,  and  look  at  the  roots  of  each. 
The  roots  of  the  Daisy  are  all  fine 
fibres,  starting  immediately  from 
under  the  leaves,  but  the  Plantain 
(p.  170)  has  one  thick  long  root 
growing  straight  down,  out  of  which 
come  most  of  the  fibres  ;  this  is 
called  a  tap-root.  The  thick  hard 
part  of  the  Dandelion  root  is  a  tap- 
root growing  downwards,  but  its 
upper  part  lies  near  the  surface  of 
the  ground,  and  carries  buds,  from 
which  fresh  stems  will  rise ;  it  is,  in  fact,  considered  an 
underground  part  of  a  stem — not  a  true  root :  its  name  is 
a  root-stock.  In  the  Potato  (p.  171)  we  find  hard  fleshy 
masses,  containing  several  eyes,  or  buds,  out  of  which 
the  next  year's  plants  would  grow ;  these  are,  in  fact, 
potatoes,  and  are  swollen  stems  or  tubers.  The  Turnip 
root  spreads  out  into  a  large  round  head,  a  great  part  of 
which  pushes  up,  and  appears  above  ground,  while  the 
fibres  hang  down  from  it  below ;  this  is  an  enlargement 
of  the  root  itself,  the  globular  root.  The  bulb  of  the 
Crocus  is  a  true  root-stock,  having  buds  concealed 
under  scales.  The  root-stocks  of  the  Lily  of  the 


Daisy. 


I/O      ANIMAL  AND   VEGETABLE  KINGDOMS. 

Valley  (p.  171)  spread  sideways  underground,  and  throw 
up  the  fresh  growths  from  their  buds. 

We  thus  see  there  exist  great  variations  in  the  forms 
of  roots,  fibres  only,  which  may  be  quite  simple,  like 
hairs,  or  branched,  as  in  grass-roots,  or  large  and  woody, 
as  in  the  roots  of  trees,  tap-roots. 

For  stems  and  branches,  let  us  add  to  our  collection 


some  Bind-weed  or  garden  Convolvulus,  Bryony,  Virginia 
Creeper,  and  a  Rose  branch.  But  first  we  must  step  out- 
side, and  look  at  some  trees  which  we  cannot  bring  in. 
On  p.  172  is  a  young  Spruce  Fir  which  would  make  a 
capital  Christmas-tree.  Its  central  stem  is  as  straight  as 
an  arrow  from  foot  to  tip,  and  the  branches  are  thrown 
out  from  its  sides  regularly  all  round.  How  different  it  is 


DIFFERENT  FORMS  OF  ROOT,   ETC.          I/I 


Turnip. 


Lily  of  the  Valley. 


1/2      ANIMAL   AND    VEGETABLE  KINGDOMS, 

from  an  Oak,  which  has  no  special  leading  shoot  in  the 
centre,  but  whose  branches  divide  up  continually  into 
smaller  and  smaller  forks  and  twigs,  until  they  make  a 


sort  of  round  head  to  the  tree.  Both  these  forms  of 
growth  are  common  among  plants  large  and  small. 
The  Buttercup,  you  see,  branches  like  the  Oak  tree,  but 
Mullein  and  Hollyhock  plants  grow  up  with  side-branches 


TRAILERS  AND    CREEPERS. 


173 


round  a  leading  shoot.  The  Buttercup  and  Mullein  stems 
are  strong  enough  to  stand  upright,  but  our  three  next 
specimens  are  not,  and  take  different  ways  of  helping 
themselves  up.  The  Convolvulus  trails  on  the  ground 
until  its  stem  touches  some  support,  when  it  twines  itself 


Stem  of  Convolvulus. 


Virginia  Creeper. 


round  and  runs  up  it,  growing  spirally.  The  Bryony  or 
Pea  (p.  174)  puts  out  from  the  side  of  its  leaf  short  green 
threads  called  tendrils,  which  curl  round  any  support  they 
can  find,  and  so  hold  up  the  main  stem ;  but  the  tendrils 


1/4      ANIMAL  AND    VEGETABLE  KINGDOMS. 


of  the  Virginia  Creeper  may  behave  quite  differently. 
Instead  of  twisting  round  a  support,  they  grow  straight 
out  till  they  touch  a  wall,  or  something  to  which  they 
can  attach  a  little  sucker  at  their  tip.  As  soon  as  this 
is  fast,  the  tendril  shortens  itself  up  into  a  tight  coil,  so 
drawing  the  main  stem  close  to  the  wall.  The  Rose 
prickles  also  help  the  plant  to  climb,  as  it  thrusts  up  its 
slender  shoots  through  other  bushes. 

Leaves  have  endless  varieties  of  shape,  and  perhaps 
a  walk  through  the  kitchen  garden  will  serve  as  well  as 
anything  to  show  a 
number  of  them.  Look 
at  the  large,  juicy  leaves 
of  the  Cabbage,  folded 
one  outside  another  over 
the  heart;  the  long, 
slender  leaves  of  the 
Onions ;  the  handsome, 
heart-shaped  leaves  of 
the  Scarlet-runners  ;  the 
notched  leaves  of  Straw- 
berries ;  the  soft,  plumy 
leaves  of  Carrots  ;  and 
the  light,  leaf-like 
feathers  of  Asparagus. 
But,  whether  large  or 
small,  pointed  or  round, 
thick  or  thin,  whole 
or  cut,  these  all  have 
one  thing  in  common,  and  that  is  their  green  colour, 
which  is,  as  we  shall  see  presently,  of  the  greatest 


Tendrils  of  Pea. 


LEAF  VARIETIES.  175 

importance  to  the  health  and  usefulness  of  the 
plants. 

In  plants  that  send  up  a  main  stem  and  branches,  the 
leaves  usually  grow  upon  these,  sometimes  sitting  close 
to  the  branch,  like  the  upper  leaves  of  Honeysuckle,  or 
more  often  joined  to  it  by  a  leafstalk  (called  a  petiole) ; 
but  many  plants  have  no  obvious  main  stem.  Look  at 
the  leaves  of  a  Daisy  (p.  169);  they  lie  in  a  flat  rosette 
upon  the  ground,  each  one  growing  directly  from  the 
root-stock,  from  which  the  flower  stalks  also  rise.  Straw- 
berry leaves  mostly  grow  straight  out  of  the  root-stock, 
but,  as  they  have  long  leafstalks,  they  make  a  tuft  and 
not  a  rosette.  Some  plants  have  both  root-leaves  and 
stem-leaves,  like  the  great  Ox-eye  daisy,  whose  root-leaves 
are  broad  and  set  on  long  stalks,  while  the  stem-leaves 
are  narrow  and  have  no  stalks.  A  different  arrangement 
is  shown  in  the  leaves  of  Grass,  the  lower  part  of  which 
is  wrapped  round  the  grass  stem  like  a  sheath. 

Daffodils  (p.  187),  Hyacinths,  Lilies,  and  many  others 
send  up  their  flower  stems  in  the  same  way  from  the 
centre  of  a  sheath  of  leaves. 

Now  we  come  to  the  flowers  themselves,  and  the 
arrangements  in  which  they  grow,  of  which  we  can  find 
plenty  of  varieties  in  the  fields.  The  bright  scarlet  Poppy 
carries  its  flowers  singly,  one  on  the  end  of  each  main 
stem  (p.  176),  while  the  little  red  Pimpernel  also  has 
separate  single  blossoms  ;  but  instead  of  being  at  the  end 
of  stems,  their  flower  stalks  each  grow  out  where  a  leaf 
joins  the  stem — in  the  axil  of  the  leaf,  as  we  say.  The 
flowers  of  the  Plantain  (p.  176)  are  crowded  closely  together 
all  along  a  spike,  and  another  kind  of  spike  may  be  seen 


1 76      ANIMAL  AND    VEGETABLE  KINGDOMS. 


in  the  catkins  that  hang  on  the  Willow  trees.  We  might 
call  the  flowers  of  the  Cuckoo-flower  a  spike,  too  ;  but 
as  each  blossom  is  set  on  a  flower  stalk,  or  pedicel,  the 


\ 

Flower  of  Poppy. 


whole  arrangement   is  much  freer  and   looser,  and   its 
proper  name  is  a  raceme.     A  panicle  is  like  a  raceme  in 


Cuckoo-flower.  Carrot. 

which  the  flower  pedicels  are  themselves  branched  so  as 
to  carry  more  than  one  flower  each. 


PATTERNS   OF  FLOWERS.  1/7 

The  flowers  of  Carrots,  Parsley,  and  Hemlock  show 
quite  another  pattern.  Their  flower  pedicels  all  start 
from  the  same  place,  but  the  outer  ones  are  longer  than 
the  inner,  so  that  the  top  of  the  flower  head  is  flat. 
This  arrangement  is  called  an  umbel. 

If  we  pull  a  daisy  to  pieces,  and,  separating  some  of 
the  little  yellow  things  from  its  centre,  examine  them 
with  a  magnifying  glass,  we  may  be  surprised  to  find 
that  each  is  a  complete  little  yellow  blossom  by  itself; 
and  so,  also,  though  of  a  different  shape,  are  the  little 
white  rays  which  surround  the  yellow  disk.  So,  then,  a 
daisy,  instead  of  being  one  single  blossom,  is  a  whole 
crowd  of  tiny  blossoms,  some  yellow  and  some  white, 
set  in  a  regular  order,  and  making  up  together  a  head. 
A  great  many  flowers  are  arranged  on  this  general 
pattern  —  all  the 

thistles    and    hard-        ,-\r^TK  /O  '  •  1 

heads,  and  ragworts 
and  groundsels,  the 
chrysanthemums 
and  asters  and  dan- 
delions—and many 

Daisy,  with  two  florets  separated. 

To  see  the  parts 

of  flowers  we  had  better  take  a  single  perfect  blossom, 
and  examine  it  carefully.  An  Apple  blossom  will 
do  well  to  begin  with,  and  we  will  cut  two,  as  we 
shall  need  to  pull  one  to  pieces.  Take  one  by  the 
stalk,  turn  it  upside  down,  and  look  first  at  the  out- 
side; you  will  find  that  its  outermost  covering  con- 
sists of  five  green  pieces,  something  like  thick  green 

N 


1/8      ANIMAL  AND    VEGETABLE   KINGDOMS. 

leaves  (p.  179).  This  green  covering  is  called  the  calyx, 
and  each  piece  when  separate  is  a  sepal ;  it  is  a  calyx 
of  five  united  sepals.  Within  the  calyx  come  five 
large,  thin,  delicate,  white  or  pinkish  leaves,  which  are 
called  the  corolla ;  each  separate  leaf  is  a  petal,  and 
the  calyx  and  the  corolla  together  form  the  perianth, 
Now  carefully  pick  off  all  the  petals,  and  see  what  is 
left  inside.  The  next  thing  is  a  number  of  slender, 
thread-like  stems,  each  carrying  a  small  head.  The 


Apple  Blossom. 

name  for  them  is  stamens,  the  heads  are  called  anthers, 
and  the  stems  filaments.  Cut  them  all  away  also,  and 
we  have  left  five  thicker  green  stems  joined  together 
at  their  base.  We  must  see  what  is  at  the  bottom 
of  these;  so,  with  a  sharp  pen-knife,  cut  straight 
down  the  middle,  laying  open  the  centre  of  the  flower 
as  in  the  illustration,  and  we  find  a  seed-vessel,  or 


THE  PARTS  OF  A  FLOWER.  179 

ovary,  with  five  divisions,  out  of  the  top  of  which 
grow  the  five  green  stems.  The  stems  are  called  styles, 
their  swollen  tips  are  stigmas,  the  divisions  below  con- 
taining the  seeds  are  car- 
pels, and  the  whole  organ  is 
called  the  pistil.  It  is  pro- 
perly described  as  a  pistil  of 
five  carpels,  with  five  styles 
joined  only  at  their  base. 

The  four  series  here  de- 
scribed— the  calyx,  corolla, 
stamens,  and  pistil  —  are 

,,     ,     ,       f  a         i7i  Section  of  Apple  Blossom. 

called  the  tow  floral  whorls. 

A  flower  is  said  to  be  complete,  when,  like  the  apple,  it 
has  them  all  four ;  and  regular,  when  each  of  the  sepals, 
and  each  of  the  petals,  is  like  the  rest  of  the  set. 

Compare  the  buttercup  with  the  apple  blossom.  It 
has  also  five  green  sepals,  either  spreading  in  the  same 
way  under  the  petals,  or  else  folded 
back  towards  the  stem.  Leave 
these ;  but  pull  off  the  five  (or 
more)  bright,  golden  petals,  and 
also  the  numerous  stamens,  until 
there  is  only  the  green  pistil,  which  Section  of  Pistn  and  Recep. 
we  will  cut  open  down  the  centre 
as  before.  This  time  we  find  quite  a  different  state  of 
things.  Instead  of  a  seed-vessel  divided  into  five  carpels, 
there  is  a  raised,  green  pyramid,  upon  which  sit  many 
carpels  quite  separate  from  one  another  and  without 
styles,  but  ending  in  a  sort  of  beak,  at  the  point  of  which 
is  the  stigma. 


l8o      ANIMAL   AND    VEGETABLE  KINGDOMS. 


In  this  case  the  ovary,  or  set  of  seed-bearing  vessels, 
is  said  to  be  superior,  or  set  up  above  the  calyx ; 
whereas,  in  the  apple,  it  is  inferior,  or  sunk  into  the 
swollen  top  of  the  flower  stalk,  which  is  so  continuous 
with  the  calyx  that  we  cannot  say  where  one  ends  and 
the  other  begins. 

In  the  buttercup  the  green  pyramid  is  the  enlarged 
tip  of  the  flower  stalk.  When  this  rises  above  the 
calyx,  it  is  called  the  receptacle,  and 
takes  different  forms  in  different 
flowers,  sometimes  making  a  flat 
cushion  or  disk,  and  sometimes  re- 
duced to  a  mere  ring. 

The  calyx  and  the  corolla  are 
very  different  in  different  plants, 
both  in  their  colour,  in  the  number 
of  the  sepals  and  petals,  and  in  their 
arrangement. 

The  commonest  variety  in  regular 
flowers  consists  in  their  being  joined 
together  for  some  part  of  their  length. 
Thus  in  the  Primrose  the  lower  part  of  all  the  petals 
is  joined  into  a  tube,  while  the  upper  parts  are 
widely  spread.  The  sepals  of  the  calyx  are  joined  in 
the  same  way  almost  to  the  top,  and  form  an  outer  tube. 
It  is  not  uncommon  to  find  plants  which  instead  of 
having  a  double  perianth,  that  is,  both  calyx  and  carolla, 
have  but  a  single  whorl  in  their  place  ;  and  as  it  is  diffi- 
cult to  see  which  represents  the  calyx  or  the  corolla,  it 
is  generally  spoken  of  simply  as  the  perianth.  The  Lily 
of  the  Valley  is  one  of  these  flowers  of  a  single  perianth 


Primrose  lilosson 


PETAL— STAMEN— PISTIL.  I  8 1 

which  is  united  into  a  bell  shape,  cleft  at  the  outer  edge 

into  six  points. 

In  irregular  flowers  the  variety  of  shapes  is  endless. 

Take  a  blossom  of  Sweet-pea,  or  Bean,  or  Laburnum,  or 

Broom,  which  are  all  alike,  and  count  its  petals.  There 
are  five,  of  different  sizes.  The  two 
smallest,  often  joined  together  by 
their  edges  into  a  boat  shape,  are 

UT 


Lily  of  the  Valley  Blossom  of  Sweet  Pea. 

Blossom. 

also  the  innermost;  they  are  known  as  the  keel.  On 
each  side  stand  the  two  wings,  and  over  and  outside  all 
is  the  standard,  as  it  is  called,  which  in  the  bud  was 
folded  over  all  the  rest.  If  you  carefully  pull  off  each 
of  the  petals  you  will  be  able  to  see  that  enclosed  in 
the  keel  is  a  bundle  of  ten  stamens,  nine  of  them  being 
always  joined  together,  while  one  stands  apart,  and  also 
a  pistil,  the  lower  part  of  which  consists  of  a  single  long 
narrow  carpel,  which  will  presently  develop  into  the  pod. 


1 82      ANIMAL   AND    VEGETABLE   KINGDOMS. 

For  some  other  irregular  forms,  compare  for  yourself 
the  blossoms  of  Snapdragon,  Dead-nettle,  Violet,  Orchis, 
and  Honeysuckle. 

Now  and  then  a  flower  has  no  perianth  at  all.  This 
is  the  case  with  the  tiny  blossoms  crowded  upon  a  catkin, 
arid  with  the  flowers  of  many  sedges. 

If  flowers  can  thus  dispense  with  a  perianth  altogether, 
it  is  clear  that  this,  though  the  most  showy  and  attractive 
to  insects,  is  not  the  most  essential  part.  The  real  im- 
portance of  the  flower  lies  in  the  pistil  and  stamens,  and 
their  action  upon  each  other  is  as  follows. 

Within  the  carpels  of  the  pistil  are  the  tiny  ovules  which 
are  to  become  the  future  seeds.  They  do  not  lie  about 
loose  like  stones  in  a  bag,  but  are  attached  to  the  inside 
of  the  carpel.  Ovules,  however,  cannot  develop  into 
seeds,  unless  they  are  fertilized  by  the  contents  of  the 
anthers,  or  heads  of  the  stamens.  When  the  anthers  are 

ripe,  they  open  and 
thus  let  out  fine 
grains  of  powder, 
called  pollen,  which 
is  usually  yellow. 

Ovules  of  Pea  in  Pod. 

The   pollen    grains 

are  tiny  cells,  and  when  one  reaches  the  spongy,  sticky 
stigma  of  the  pistil,  soon  there  grows  out  of  it  a  tube  which 
passes  into  the  stigma,  and  down  the  length  of  the  style 
into  the  ovary,  where  it  communicates  its  contents  into 
the  ovule.  It  is  a  beautiful  sight  to  see  through  a  micro- 
scope the  pollen  grains  putting  out  their  delicate  tubes. 

The  stamens  and  pistils  do  not  always  grow  in  the 
same  flower.  On  a  hazel  bush  we  shall  find  that  all  the 


THE  SEED.  183 

hanging  catkins  contain  stamens  only;  but  by  careful 
search  over  the  tree,  minute  crimson  tufts  may  be  found, 
which  are  the  pistil  flowers  and  will  hereafter  produce 
the  nuts.  In  willows  the  separation  goes  still  further, 
and  the  stamen  and  pistil  flowers — the  male  and  female 
catkins— grow  on  different  trees.  Even  where  stamens 
and  pistils  occur  in  the  same  flower,  the  seeds  are  found 
to  be  finer  when  fertilized  by  pollen  from  flowers  at  a 
distance,  and  you  will  be  able  to  read  in  larger  books 
of  many  exquisitely  beautiful  natural  arrangements  for 
securing  fertilization  from  distant  flowers,  of  which  there 
is  not  room  to  speak  here.  Thus  at  last  appears  the 
seed,  the  plant's  treasure,  which,  born  in  the  heart  of 
the  flower,  protected  by  all  its  envelopes,  nourished,  and 
ripened,  at  last  escapes,  either  falling  to  the  ground,  or 
carried  away  by  wind,  or  water,  or  birds,  to  grow  into 
a  new  plant. 

To  watch  the  beginning  of  this  new  growth,  we  cannot 
choose  a  better  seed  than  a  bean,  which  is  large  enough 
to  be  well  seen,  and  also  has  the  advantage  of  being 
very  familiar.  We  all  know  the  appearance  of  beans 
when  cooked  for  dinner — with  a  loose  grey  skin,  inside 
of  which  are  the  two  fat,  fleshy,  green  halves  of  the  bean, 
joined,  if  still  joined  at  all,  only  in  one  spot  of  their 
edge.  If  we  take  off  the  skin  of  a  raw  bean  and  observe 
this  joining  closely,  we  shall  see  that  it  is  made  by  a 
tiny  thing,  with  one  end  more  pointed  than  the  other, 
which  lies  between  the  two  halves  of  the  bean,  and  is 
attached  by  its  middle  to  both  of  them.  When  a  bean 
is  sown,  that  is,  placed  on  or  just  under  the  soil  where 
air  can  reach  it,  and  furnished  with  moisture  and 


184      ANIMAL  AND    VEGETABLE  KINGDOMS. 

sufficient  warmth,  it  will  begin  to  sprout,  as  we  say ;  that 
is,  this  tiny  body  will  begin  to  lengthen  at  both  ends. 
The  pointed  end  will  break  through  the  skin  of  the  seed 
and  appear  outside  as  a  little  tail,  which  is  called  the 
radicle,  and  is  the  beginning  of  the  root  of  the  plantlet ; 
while  the  other  end  will  grow  in  the  opposite  direction 
up  between  the  two  halves  of  the  seed,  and  soon  appear 


Germination  of  Bean. 

above  them ;  it  is  called  the  plumule,  and  is  the  beginning 
of  the  stem  and  leaves.  The  fleshy  parts  of  the  seed  are 
called  the  cotyledons,  and  they  are  so  fat  because  they 
are  filled  with  the  nourishment  which  the  young  plant 
requires  at  first.  As  the  plant  grows  on  and  absorbs  this 
nourishment,  the  cotyledons  shrivel  up  and  die. 

This  history  is  not  quite  the  same  for  all  plants.     In 


GROUPS   OF  FLOWERING  PLANTS. 


I85 


the  mustard  seed,  for  example,  the  cotyledons  are  small 
and  thin,  and  instead  of  remaining  on  the  ground  feed- 
ing the  plantlet,  they  grow  up  above  ground  below  the 
growing  plumule,  spread  out, 
turn  green,  and  become  the  first 
leaves  of  the  plant,  drawing  in 
nourishment  for  it  from  the  air. 
We  should  never  have  guessed 
from  the  bean  that  the  coty- 
ledons were  the  first  leaves  of  a 
plant,  had  we  not  clearly  seen 
it  in  other  plants.  Some  seeds 
contain,  besides  the  young  plant 
with  its  cotyledons,  a  separate 
store  of  nourishment. 

These  seed  leaves  are  not 
generally  like  the  later  leaves 
of  the  plant,  but  the  young  plant 
continuing  to  grow  up  between  them  begins  to  put  out 
its  characteristic  leaves  with  the  very  next  pair.  We 
often,  therefore,  cannot  recognize  what  a  seedling  will 
prove  to  be  until  its  later  leaves  have  appeared. 

All  Flowering  Plants  are  arranged  in  three  main  groups, 
and  we  find  that  the  number  of  the  cotyledons  is  one  of 
the  distinguishing  marks  by  which  they  are  recognized. 

I.  Dicotyledons. — The  bean  and  the  mustard,  as  we 
have  seen,  each  have  two  cotyledons,  as  have  also  far 
the  larger  number  of  the  flowering  plants,  and  all  our 
English  trees  except  the  fir-tree  group.  From  this  cir- 
cumstance the  name  Dicotyledons  is  given  to  the  Class. 
All  the  plants  of  this  Class  have  their  branches  and  twigs 


Mustard  Plant,  with  Cotyledons 
and  Second  Leaves. 


1 86      ANIMAL   AND    VEGETABLE  KINGDOMS. 


growing  from  buds  which  sprout  out  of  the  sides  of  the 
stems,  and  the  parts  of  their  flowers,  sepals,  petals, 
stamens,  etc.,  are  generally  arranged  in  fours,  fives,  and 
eights.  If  you  examine  wallflowers  and  primroses,  for 
instance,  you  will  find  that  the  wallflowers  have  four 
sepals  in  the  calyx  and  four  petals  in  the  corolla,  while 


Harebell  and  Snowdrop  Pla 


primroses  have  five  of  each.  The  Class  contains  many 
Orders,  with  flowers  hoth  regular  and  irregular.  Two 
of  the  largest  Orders  and  most  marked  types  are  the 
Leguminosae,  or  Pod-bearing  plants,  of  which  the  Pea- 
flower  (p.  181)  is  a  representative,  and  the  Composite 
plants,  like  the  Daisy  (p.  177),  consisting  of  many  small 
florets  crowded  upon  one  receptacle. 


THE  SECOND  DIVISION. 


187 


II.  Monocotyledons. — Crocuses  and  Snowdrops  do  not 
put  up  a  pair  of  little  leaves  like  the  Mustard,  but  begin 
with  a  single  cotyledon,  and  so  belong  to  the  Class  of 
Monocotyledons.  These  rarely  have  true  branches,  but 
their  fresh  shoots,  instead  of 
budding  out  of  the  side  of 
the  stem,  spring  out  of  the 
middle  or  heart  of  the  plant, 
and  the  leaves  or  leaf-stems 


frequently  form  a  sheath  round  the  flower  stem.     The 
parts  of  the  flowers  are  generally  in  threes  or  sixes. 

Here  are  pictures  of  a  Harebell  and  a  Snowdrop,  which 
show  characteristic  differences  between  the  two  Classes. 
The  harebell,  which  belongs  to  the  Dicotyledons,  has 


1 88      ANIMAL  AND   VEGETABLE  KINGDOMS. 


both  calyx  and  corolla  divided  into  five  parts,  and  con- 
tains five  stamens,  and  the  little  plant  grows  up  with 
slender  branches  coming  out  of  the  sides  of  the  stems. 
The  snowdrop,  on  the  other  hand,  has  three  outer  sepals 
of  pure  white,  three  short  inner  ones  tipped  with  green, 

and  six  stamens, 
and  the  flower-stem 
grows  up  in  the 
innermost  heart  of 


Palm  Tree.       .  Germination  of  Spruce  Fir. 

the  plant,  the   lower   parts   of   the   leaves   wrapping   it 
round  like  a  sheath. 

This  Class  includes  most  of  the  plants  raised  from 
bulbs,  such  as  Hyacinths,  Tulips,  Daffodils,  Lilies,  and 
also  Orchises,  Arums,  Rushes,  Reeds,  and  the  important 
Order  of  Grasses,  which  not  only  feed  our  cattle,  but 
afford,  in  the  form  of  Wheat,  Barley,  Rice,  Maize,  etc., 


FLOWERLESS  PLANTS.  189 

a  great  part  of  our  own  food  supply.  A  characteristic 
tree  of  the  Class  is  the  palm  tree,  which  carries  a  single 
tuft  of  great  leaves  at  the  top  of  the  generally  un- 
branched  stem. 

III.  Coniferce. — The  Cone-bearing  trees  are  a  single 
Order  containing  all  the  Fir  or  Pine  trees,  Cypress,  Cedar, 
Larch,  Juniper,  Yew,  etc.  Baby  fir  trees,  some  of  the 
most  fascinating  of  young  growths,  instead  of  being 
content  with  two  cotyledons,  often  put  out  a  whole  ring 
of  them,  and  the  Coniferse  are  also  distinguished  by 
their  ovules  and  seeds  being  quite  naked,  instead  of 
being  enclosed  in  an  ovary  or  seed-vessel,  like  those  of 
both  the  other  Classes. 

Flowerless  Plants. — The  whole  of  what  has  been 
said  as  yet  applies  entirely  to  Flowering  Plants,  which 
constitute  the  highest  division  of  the  Vegetable  Kingdom. 
The  Flowerless  Plants,  which  have  no  true  stamens  or 
pistils,  and  therefore  do  not  form  seeds  in  the  same 
way  at  all,  are  a  more  difficult  and  advanced  study, 
and  we  must  here  be  content  with  learning  that  they 
consist  of  Club-mosses,  Horse-tails,  curious  green  plants 
which  in  wet  places  often  grow  to  a  considerable  size ; 
Ferns,  Mosses,  Liverworts,  which  spread  their  filmy 
leaves  among  moss  on  damp  lawns;  Lichens,  which 
sometimes  grow  as  grey  tufts  on  the  bark  of  trees, 
sometimes  form  cloudy  patches  of  various  colours  on 
old  stones  and  rocks  and  roofs;  Funguses,  including 
not  only  mushrooms  and  the  many  plants  that  we  call 
toadstools,  but  all  the  various  growths  to  which  are 
given  the  names  of  mould,  yeast,  dry  rot,  smut  and 
rust  in  wheat,  and  others ;  Alg?e,  to  which  belong  all 


1 90      ANIMAL   AND   VEGETABLE  KINGDOMS. 

sea-weeds  and  some  fresh-water  weeds ;  and,  finally, 
Bacteria,  minute  microscopic  fungal  plants,  which  grow 
and  swarm  in  living  and  dead  animals  and  plants,  and 
are  the  cause  of  many  diseases,  as  well  as  being,  in  many 
cases,  very  useful  scavengers. 


CHAPTER   X. 

PLANT    LIFE. 

ALTHOUGH  there  seems  to  be  a  likeness  between  some  of 
the  clearly  lower  forms,  yet,  on  the  whole,  life  in  plants  is 
very  different  from  that  of  animals.  Plants  have  neither 
heart,  brain,  nerves,  nor,  in  most,  power  of  moving  about ; 
and  yet  life  of  some  sort  there  certainly  is,  for  plants  are 
born,  feed,  digest,  grow,  bring  forth  young,  become  sick, 
and  then  part  with  their  lives  and  die.  They,  and  they 
only,  can  feed  directly  upon  the  earth  and  the  air,  and 
in  their  bodies  the  nourishment  is  changed  into  food 
which  animals  can  digest  and  live  upon ;  so  that  without 
plants  all  animal  life  would  speedily  come  to  an  end, 
for,  even  those  creatures  which  eat  other  animals  would 
find  that  their  prey  all  died  of  starvation. 

One  of  the  mysteries  of  plant  life  is  the  difficulty  of 
knowing  in  what  a  single  plant — a  single  life — consists. 
We  may  have  a  plant  grown  from  a  single  seed,  and  we 
feel  inclined  to  say,  " This,  at  least,  is  one''  But  a 
gardener  may  take  our  plant  and  cut  it  into  a  score  of 
pieces,  every  one  of  which  when  planted  will  grow  roots 
for  itself,  and  carry  on  all  the  business  of  plant  life.  Are 
they  many  plants,  or  one?  For  they  all  grew  from  a 
single  seed. 


IQ2      ANIMAL   AND    VEGETABLE  KINGDOMS. 

We  may  go  on  thus  propagating  a  plant  by  cuttings 
for  a  long  time,  but  there  is  no  real  fresh  spring  of  life 
in  cuttings  ;  they  are  but  divisions  of  the  old  life,  and 
at  last  it  comes  to  an  end  :  the  strain  wears  out,  as  we 
say,  and  dies.  The  only  beginning  of  real  new  life  in 
plants  is  the  seed,  the  young  one  born  of  older  parents, 
and  starting  afresh. 

Duration  of  Life. — Plants  differ  very  much  in  the 
length  of  their  life.  Some  spring  up  from  seed,  grow  to 
their  full  size,  blossom,  and  bear  seed  once,  and  then 
die,  all  within  a  single  season.  Many  of  our  garden 
flowers  are  among  these  plants  of  a  year,  or  annuals,  as 
they  are  called.  Sweet-peas,  for  instance,  have  to  be 
sown  afresh  every  year,  for  when  autumn  comes,  and 
their  blooming  is  over,  they  die  of  old  age,  and  their 
dead  bodies  decay  and  rot  into  the  ground,  leaving 
nothing  behind  them  but  the  baby  seeds  which  are  to 
grow  into  the  next  generation. 

Some,  such  as  turnips,  radishes,  etc.,  take  t\vo  years 
to  grow  to  maturity  and  do  their  seed-bearing ;  and 
others,  like  the  banana,  may  grow  on  for  many  years 
before  they  blossom  and  bring  forth  seed ;  but  when  this 
one  event  of  their  lives  is  over,  they  also  often  die. 

Finally,  we  come  to  the  very  numerous  plants  which 
are  not  exhausted  to  death  by  their  first  seeding,  but  are 
able  to  go  on  year  by  year  putting  forth  flowers  and 
seeds.  In  this  case  they  either  die  down  to  the  root- 
stock  every  year,  springing  up  again  with  new  vigour, 
like  the  daisy,  or  else  the  stem  and  branches  remain, 
throwing  out  fresh  buds  in  spring  time,  like  the  oak. 

When  the  old  leaves  hang  on  the  tree  till  after  the 


TISSUES  OF  PLANTS. 


193 


young  ones  have  appeared,  as  in  holly,  laurel,  and  most 
fir  trees,  they  are  called  evergreens ;  but  many,  as  we  know, 
lose  their  leaves  in  autumn,  and  stand  all  the  winter,  look- 
ing bare  and  dead,  waiting  for  the  next  season's  growth. 

Tissues  of  Plants. — If  we  examine  the  tissues  or 
substance  of  plants  with  a  microscope,  we  shall  find  that 

IE 


Cellular  Tissue.  Woody  Tissue. 

they  are  made  up  of  little  cells,  each  of  which  consists 
of  a  bag  or  case  called  the  cell-wall,  and  of  the  contents 
of  the  cell,  which  are  generally  half  liquid  in  living  cells. 
The  cells  can  sometimes  be  easily  divided  from  each 
other,  like  those  in  the  pulp  of  an  orange,  where  they 
are  large  and  dis- 
tinct, but  they  are 
often  crowded 
closely  and  com- 
pactly together. 

Generally  the 
cells  are   round,  or  Vascular  Tissue, 

nearly  so,  and  when  living  each  cell  has  a  small  quantity 
of  the  living  substance,  called  protoplasm,  enclosed  by 
the  cell-wall.  The  contents  of  the  cells  are  not  com- 
pletely separated  by  this  thin  wall,  but  are  connected  by 
very  fine  threads  of  protoplasm  running  through  the  walls. 
When  cells  become  old  they  often  lose  their  protoplasm 
and  so  become  dead,  the  wall  changing  from  its  original 

o 


IQ4      ANIMAL  AND    VEGETABLE  KINGDOMS. 

cellulose  to  a  woody  character ;  the  walls  at  the  same  time 
become  more  or  less  thickened  and  sculptured.  If  now 
the  end  walls  break  down,  then  long  tubes,  called  vessels, 
are  formed,  and  these,  though  dead,  are  not  useless,  for 
it  is  through  their  cavities  all  the  water  needed  by  the 
plant  ascends  from  the  soil  to  the  leaves.  These  vessels 
are  also  found  in  the  veins  of  leaves,  and  multitudes  of 
such  vessels,  along  with  woody  fibre,  give  strength  to  the 
trunk  of  a  tree. 

Feeding  of  Plants.— This  is  the  way  in  which  plants 
feed.  The  delicate  cells  of  the  rootlets  finding  in  the 
ground  the  mineral  food  that  they  want 
dissolved  in  water,  draw  it  through  the 
walls  into  their  cells,  from  which  it  passes 
on,  drawn  up  from  cell  to  cell  in  the  same 
manner,  through  the  stem  and  branches 
until  it  reaches  the  leaves.  As  yet  it  is 
almost  in  the  same  condition  as  when  it 
was  taken  from  the  soil;  but  green  leaves 
act  as  the  stomach  of  the  plant  and  digest 
the  food,  converting  it  into  various  substances,  after  which 
it  passes  down  again  and  is  distributed  through  the  cells  as 
is  needed.  The  healthy  and  vigorous  leaves  also  absorb 
from  the  air  carbonic  acid  gas,  and  separating  the  carbon 
and  oxygen  of  which  it  is  made,  return  some  of  the 
oxygen  into  the  air,  and  use  the  carbon  for  nourishment. 
The  faded  and  decaying  parts  of  plants,  on  the  other 
hand,  give  off  a  little  carbonic  acid,  and  so  also  do  the 
blossoms,  and  the  green  leaves  at  night ;  but  the  quantity 
is  so  small  as  to  be  absolutely  insignificant  compared 
with  the  oxygen  supplied  by  growing  leaves.  As, 


HOW  PLANTS  LIVE.  195 

however,  the  leaves  only  give  out  oxygen  in  the  light,  it 
follows  that  at  night  or  in  the  dark  there  is  nothing  to 
set  against  the  carbonic  acid.  Animals,  you  will  re- 
member, also  breathe  out  carbonic  acid  and  take  in 
oxygen,  so  that  a  person  who  sleeps  at  night  in  a  small 
room  crowded  with  plants  will  have  a  little  less  fresh 
air  to  breathe,  because  the  plants,  as  well  as  himself, 
are  using  the  oxygen  and  helping  to  fill  the  room  with 
carbonic  acid.  By  day,  however,  and  especially  in  strong 
sunlight,  just  the  reverse  is  the  case;  the  leaves  are  then 
rapidly  absorbing  carbonic  acid  and  throwing  out  so 
much  oxygen  that  the  plants  are  helping  to  purify  the 
air  and  make  it  fit  for  animals  to  breathe  over  again. 
The  moral  is  — keep  growing  plants  in  your  sitting-rooms, 
but  do  not  crowd  them  into  your  bedrooms. 

Take  two  glass  jars  or  bottles  filled  to  the  brim  with 
spring  water,  and  after  plunging  into  each  of  them  a 
handful  of  a  fresh  water-weed,  turn  them  each  care- 
fully mouth  downwards  into  a  basin  of  water,  and  then 
put  one  in  the  sunshine  and  the  other  into  a  dark 
cellar.  If  we  examine  them  both  at  the  end  of  an  hour 
or  two  we  shall  find  no  change  in  that  brought  from  the 
cellar,  the  leaves  having  done  no  work  in  the  dark ;  but 
in  that  which  has  had  the  sun  upon  it  we  shall  see 
numerous  small  bubbles  formed  all  over  the  leaves  and  also 
at  the  top  of  the  bottle,  which,  if  collected  after  a  time 
and  tested,  will  prove  to  be  pure  oxygen  gas.  In  this 
case  the  leaves  have  not  indeed  drawn  their  carbonic 
acid  from  the  air ;  but  they  have  found  some  dissolved 
in  the  water,  and  have  thrown  off  the  oxygen  in  it, 
appropriating  the  carbon  as  food. 


196      ANIMAL   AND    VEGETABLE  KINGDOMS. 

The  principal  substance  into  which  the  food  of  the 
plant,  whether  procured  from  air,  water,  or  the  soil,  is 
digested  in  the  leaves,  is  starch,  or  sugar,  which  are 
forms  of  the  same  material.  The  cell  walls  are  made 
of  the  starch-like  body,  cellulose,  plenty  being  wanted 
for  building  fresh  cells  when  the  plant  is  growing,  while 
the  starch,  in  little  solid  grains,  is  found  stored  up,  either 
in  roots  or  tubers,  like  the  potato,  from  which  the  plant 
means  to  nourish  itself  when  it  starts  growing  next 
year,  or  in  seeds,  where  it  is  deposited  for  the  food  of 
the  young  plants,  and  from  which  we  take  it  for  our  food 
in  the  shape  of  wheat,  rice,  beans,  peas,  etc.  The  sugar, 
which  is  the  form  of  the  material  that  can  be  dissolved 
in  water,  occurs,  as  we  know,  in  the  cells  of  sugar-cane 
and  of  sweet  ripe  fruits. 

But  different  plants,  each  according  to  their  own  powers, 
secrete  out  of  their  food  many  other  substances  than 
these.  Some  make  wax  or  oils,  such  as  linseed  oil, 
castor  oil,  olive  oil,  and  others ;  some  produce  resin  and 
turpentine,  some  find  lovely  colouring  materials  or  sweet 
scents  for  their  flowers,  some  give  valuable  medicines, 
such  as  quinine,  others  deadly  poison,  like  strychnine. 

All  these  vegetable  products  are  deposited  in  the  plant 
cells,  and  sometimes  there  are  also  deposits  made  of 
mineral  substances.  In  many  trees,  for  instance,  the 
cells  in  the  middle  of  the  trunk  and  old  branches  become 
gradually  solid,  filled  up  with  mineral  matter,  and  unable 
to  do  their  cell  work  any  more.  But  a  fresh  ring  of 
wood  grows  every  year  on  the  outside  of  these,  enlarging 
the  size  of  the  tree,  and  only  through  the  outer  living 
part  are  the  processes  of  life  carried  on  :  so  that  an  old 


THE  DIET  OF  PLANTS. 


I97 


Timber  cut  across,  showing  rings,  and 
crack  during  drying. 


tree  is  something  like  a  coral  reef,  in  which  the  new 
living  coral  is  growing 
upon  a  foundation  of 
older  dead  coral.  In- 
deed, we  know  that  trees 
quite  hollow  inside  can 
go  on  growing  and  put- 
ting out  leaves  if  the 
outside  rings  of  sap  wood 
are  left.  The  solid  tim- 
ber of  the  tree  centre  is 
called  heart  wood,  while 
the  younger  outside  part  is  sap  wood.  When  a  tree  is 
cut  down,  we  can  often  see  on  the  cut  surface  of  the 
trunk  the  successive  rings  of  wood, 
and,  as  one  is  generally  made  every 
year,  we  can,  by  counting  them,  tell 
fairly  the  age  of  the  tree. 

Only  green  leaves  or  green  parts 
of  plants  can  digest  unorganized 
matter  or  the  salts  of  the  earth. 
What  happens  then  to  plants  which 
have  no  green  parts  ?  They  have  to 
live,  just  as  we  do,  on  organized 
food,  some  growing  as  parasites  on 
living  plants,  either,  like  the  common 
dodder  of  our  heaths,  drinking  in  the 
sap  of  their  stems  and  branches,  or 
else,  like  broomrape  and  many 
others,  getting  nourishment  from  J 'odder  on  heather, 
their  roots ;  others  feeding  on  dead  and  decaying 


198      ANIMAL  AND    VEGETABLE   KINGDOMS. 


organized  matter,  like  the  mould  plant  and  many  other 
species  of  fungus. 

A  few  plants  vary  their  diet  by  catching  small  insects 
and   sucking    their  juices. 
The  sundew  that  grows  in 
boggy  ground  is  one  of  the 
most  familiar  of  these,  and 
may  be   easily  known  by 
its    leaves    covered     with 
long  red  sticky  tentacles. 
When  an  insect  alights  on 
the   leaf,  attracted  by  the 
sweet    juice    secreted,    it 
irritates     and     is     caught 
by  these  tentacles    which 
slowly    bend     towards    it 
and   close  over  it, 
at    the    same   time 
pouring  out  a  fluid, 
which,  like   gastric 
juice,    digests     the 
insect,     when     the 
nourishment  it  con- 


Sundew  plant,  and  one  leaf  closing  over  fly. 


tains  is  absorbed  into  the  substance  of  the  plant.  If 
offered  small  pieces  of  raw  meat  the  sundew  will 
accept  and  digest  them  in  the  same  manner. 


PART   II. 
THE    FORCES    OF    NATURE. 

CHAPTER   XI. 

FORCES     AT     WORK. 

WHEN  we  look  round  the  world  in  which  we  live,  we 
immediately  recognize  that  other  things  move  besides 
those  that  are  alive.  We  are  quite  accustomed  to  many 
of  these  movements ;  when  they  always  take  place  under 
the  same  circumstances  we  come  to  reckon  upon  them 
and  use  them.  Babies  learn  them  as  they  begin  to  notice 
what  goes  on,  and  by  the  time  we  are  old  enough  to 
think  for  ourselves  we  treat  them  as  matters  of  course, 
and  say,  "  We  know  them ;  they  are  matters  of  common 
experience."  Perhaps  we  are  even  so  mistaken  as  to 
think  we  know  all  about  them. 

Now,  let  us  try  to  observe  and  study  a  little  more 
closely. 

Gravitation. — Suppose  we  have  a  picture  standing 
on  a  smooth  narrow  shelf  and  leaning  against  the  wall. 
It  is  not  unlikely  that,  coming  one  day  into  the  room,  we 
may  find  it  on  the  floor. 

What  made  it  fall  ?    Some  one  begins  to  explain  to 


200  THE  FORCES  OF  NATURE. 

us  that  it  had  not  a  sufficiently  safe  support  to  prevent 
it  from  falling.  Yes ;  but  why  does  it  want  preventing  ? 
Does  it  like  the  floor  better  than  the  shelf?  It  is  not 
alive;  what  made  it  begin  moving  at  all?  Why  do 
things  tumble  down  when  they  are  not  prevented? 
These  questions  seem  to  cause  great  amusement,  and 
we  are  told,  "  Why,  of  course  they  do ;  they  can't  help 
it."  Why  can't  they  help  it  ?  "  We  don't  know  why ; 
but  they  always  do." 

No  one  who  had  studied  the  subject  for  a  lifetime 
could  possibly  make  a  better  or  more  scientific  answer. 
They  always  do,  and  u<e  do  not  know  why.  There 
certainly  is  a  tendency  in  things  to  come  to  the  ground 
— that  is,  to  get  as  near  as  possible  to  the  earth,  or 
rather  to  the  centre  of  the  earth,  for  they  will  not  rest 
at  its  surface  if  they  have  a  chance  of  getting  lower  down 
into  it. 

Can  we  find  other  movements  to  compare  with  this 
inexplicable  habit  of  tumbling  down  ?  If  we  turn 
from  the  earth  to  the  heavens  we  find  a  precisely 
similar  state  of  things  on  a  vast  scale.  For  we  learn 
from  astronomers  that  one  of  the  main  influences  on  the 
movements  of  the  stars  is  a  tendency  that  they  have  to 
approach  each  other.  They  seem  to  have  an  attraction 
for  each  other. 

In  the  same  way  two  balls  suspended  near  each  other 
tend  to  approach  each  other,  and,  in  fact,  careful  obser- 
vation and  experiment  show  that  all  material  substances 
have  the  same  tendency,  and  will  come  together  if  they 
can.  Two  objects  of  the  same  weight,  if  free  to  move, 
travel  towards  each  other  at  the  same  pace,  and  so 


THE  FORCE   OF  GRAVITATION'.  2OI 

would  meet  at  a  point  halfway  between  them ;  if,  how- 
ever, one  is  much  heavier  than  the  other,  its  movements 
are  slower  in  proportion,  and  it  would  not  have  gone 
so  far  before  meeting  with  the  lighter  one  which  was 
hastening  towards  it.  The  moon  is  lighter  than  the 
earth,  and  is  always  trying  to  meet  it.  They  do  not  rush 
together,  nor  do  the  earth  and  the  sun,  because  another 
force  is  present  preventing  this. 

Returning  to  our  fallen  picture,  we  can  now  see  that 
if  the  picture  and  the  earth  were  trying  to  approach 
each  other,  then  the  instant  the  obstacle  of  the  shelf  was 
got  over,  the  little  picture  hurried  to  the  earth,  while 
the  huge  earth  had  made  such  a  very  small  movement 
before  they  met  as  to  be  quite  inappreciable.  Moreover, 
the  earth  being  enormously  larger  than  any  of  the 
movable  things  upon  its  surface,  we  are  never  able  to 
recognize  its  movements  to  meet  them,  and  so  can  only 
see  that  the  things  have  a  tendency  to  "come  to  the 
ground  " — to  "  tumble  down." 

Now,  men  have  noticed  this  tendency  of  things  to 
come  to  each  other,  and  though  the  cause  of  it  is  un- 
known to  us,  they  have  given  this  unknown  cause  a 
name.  They  call  it  the  Force  of  Gravitation.  They 
have  not  explained  it  by  giving  it  a  name.  Note  clearly 
that  we  know  no  more  than  before  about  its  nature,  or 
how  it  acts,  or  why  the  presence  of  one  body  should 
make  a  difference  to  another  that  is  at  a  distance  from 
it.  We  can  observe  further  facts  about  the  tendency,  and 
the  conditions  under  which  it  acts ;  for  instance,  that  it 
is  not  equally  strong  in  objects  of  the  same  size,  if  their 
weights  differ,  and  that  it  is  stronger  at  short  distances 


2O2  THE  FORCES  OF  NATURE. 

than  at  long  ones,  and  we  are  able  to  set  down  in  figures 
how  the  strength  and  distance  vary.  But  all  this  is  not 
explaining  what  the  force  is,  nor  the  reason  that  it  acts 
as  it  does. 

Gravitation,  the  endeavour  of  things  to  come  to  each 
other,  is  not  the  only  source  of  energy  in  natural  objects, 
else  everything  would,  sooner  or  later,  be  stuck  together 
in  a  vast  heap.  Other  tendencies  there  are,  some  of 
which  resist  gravitation,  and  help  things  to  keep  apart ; 
we  see  with  great  interest  that  such  is  the  case,  but  of 
the  causes  of  any  one  of  them  we  know  very  little 
indeed. 

But  it  is  quite  time  to  pick  up  our  picture  from  the 
ground.  They  have  got  together;  they  are,  so  far, 
satisfied  for  the  time  with  regard  to  their  gravitation, 
their  mutual  attraction.  You  pick  up  the  picture.  By 
your  muscular  power  you  resist  and  overcome  the 
gravitation,  and  separate  the  picture  from  the  ground, 
but  the  weight  of  it  upon  your  arms  is  the  measure  of 
its  resistance  to  being  lifted  up ;  that  is,  of  the  attraction 
which  the  earth  has  for  it.  You  hang  it  up  by  an  iron 
wire  to  a  hook  on  the  wall,  and  the  wall,  the  hook,  and 
the  wire  resist  the  gravitation,  and  keep  the  picture  in 
its  place  on  the  wall  in  spite  of  the  constant  and  steady 
pull  towards  the  earth. 

Cohesion. — Here,  then,  we  have  found  another  force 
in  the  wire.  It  is  the  force  that  holds  its  particles,  or 
molecules  (as  they  are  called),  firmly  together,  and 
prevents  them  from  being  pulled  apart  by  the  picture's 
weight.  It  is  called  the  Force  of  Cohesion,  or  molecular 
attraction.  The  minute  molecules  of  the  wire  are  so 


METHODS  OF  RESISTING   GRAVITATION.    2O3 

strongly  attracted  to  each  other,  and  cling  together  so 
firmly,  that  they  cannot  easily  be  separated. 

Cohesion  is  not  the  same  thing  a.s  gravitation,  for  it 
acts  only  when  the  molecules  are  very  close  together 
indeed.  Suppose  you  cut  through  the  wire,  and  then 
press  its  cut  ends  closely  together  again.  They  will  not 
cohere ;  you  cannot  get  the  molecules  near  enough.  The 
moment  you  leave  go,  down  will  go  the  picture,  for  the 
cohesion  which  held  the  wire  together  is  interrupted, 
and  the  gravitation,  no  longer  resisted,  seizes  upon  the 
picture,  and  carries  it  down  to  the  ground. 

Here  we  have  seen  three  powers  opposing  one  another  : 
first  gravitation,  then  cohesion,  then  vital  power,  or  the 
power  in  the  muscles  of  a  living  creature,  which  first 
resisted  the  gravitation  by  picking  up  the  picture,  then 
by  hanging  it  on  a  wire  employed  cohesion  to  continue 
the  resistance,  and  afterwards,  destroying  its  own  work, 
broke  the  cohesion  by  cutting  the  wire,  and  let  the 
gravitation  have  its  way  again. 

Heat. — There  are  other  ways  besides  cutting  in  which 
the  cohesion  of  the  wire  may  be  overcome.  If  the  wire 
were  exposed  to  very  great  heat,  some  part  of  it  might 
melt,  and  the  gravitation,  ever  active,  would  instantly 
get  the  picture  down  to  the  ground.  Heat  is  the  agency 
called  in  this  time,  and  heat  and  cohesion  are  old  enemies, 
always  battling  together,  as  we  shall  have  occasion  to 
see  again  presently. 

Chemical  Affinity. — Or  the  wire  may  escape  both 
cutting  and  fire,  and  hang  on  for  years  in  the  same  spot. 
The  picture  remains  in  its  quiet  corner.  Is  it  at  rest  ? 
Apparently.  The  gravitation  towards  the  ground  is  still 


204  TH%  FORCES  OF  NATURE. 

as  ready  as  ever,  but  the  cohesion  of  the  wire  opposes 
it,  and  rest  in  the  world  of  nature  only  means  that 
opposing  forces  are  evenly  balanced,  so  that  neither 
can  overcome  the  other.  People  go  about  their  business 
and  their  pleasure,  and  change,  and  grow  old ;  and  if 
any  heed  is  sometimes  taken  of  the  old  picture  in  the 
corner,  no  one  takes  heed  of  the  old  wire.  But  at  last, 
some  day  or  some  night,  down  comes  the  picture  with 
a  crash.  The  ever-active  gravitation  has  won  ;  what  has 
weakened  the  cohesion?  Some  one  picks  it  up  and 
says,  "  Why,  the  old  wire  is  eaten  through  with  rust." 

Here  you  are  to  be  introduced  to  a  new  agency. 

You  must  know  that  iron  and  oxygen  have  a  strong 
liking  for  each  other,  and  that  they  will  come  together 
when  they  get  the  chance ;  very  slowly  if  the  oxygen  is 
contained  in  dry  air,  more  rapidly  if  there  is  moisture 
as  well.  But  the  iron  and  oxygen  are  not  satisfied 
merely  to  be  near  each  other  as  if  they  were  acted  upon 
by  gravitation;  nor  do  their  molecules  simply  cohere 
together,  each  remaining  what  it  was  before.  No ;  they 
combine  together  to  form  a  new  substance,  which  is 
neither  iron  nor  oxygen,  though  it  is  made  of  them  both  ; 
it  is  called  oxide  of  iron,  or,  more  familiarly,  rust.  It 
clearly  has  not  the  same  properties  as  iron,  since,  for 
one  thing,  its  cohesion  is  much  less  strong,  and  when 
much  of  the  iron  is  converted  into  rust,  the  gravitation 
does  not  meet  with  enough  resistance,  and  wins  the 
day. 

This  tendency  of  substances  to  combine  together  and 
so  form  new  substances  is  called  Chemical  Attraction 
or  Chemical  Affinity,  and  the  examination  of  these 


THE  MEANING   OF  "FORCE."  2O5 

combinations,  and  of  the  conditions  under  which  they 
take  place,  is  the  Science  of  Chemistry. 

Electricity.—  One  other  agency  must  here  be  referred 
to.  Tear  up  a  bit  of  soft,  light  paper  into  very  small 
pieces  on  the  table,  and  then  smartly  rubbing  a  stick  of 
sealing-wax  on  your  sleeve  or  on  any  other  woollen 
substance,  bring  the  rubbed  end  near  the  bits  of  paper, 
and  you  will  see  them  rising  from  the  table  and  trying 
to  come  to  it.  There  is  clearly  something  present  resist- 
ing and  overcoming  their  gravitation,  and,  in  fact,  we 
have  here  the  first  faint  indication  of  the  wonderful  power 
of  Electricity. 

FRICTION  is  an  agency  known  only  by  the  resistance  to 
motion.  This  resistance  arises  when  the  rubbing  of  things 
against  each  other  tends  to  check  and  stop  their  motion. 
A  ball  rolled  along  the  ground  soon  slackens  and  is 
stopped  by  the  rubbing  or  friction  between  it  and  the 
ground ;  but,  if  it  is  driven  along  smooth  ice,  the  same 
energy  will  carry  it  much  further,  because  friction  is  much 
less  on  smooth,  polished  surfaces.  Friction,  either  of 
solid  things,  or  of  water,  or  of  air,  must  be  taken  into 
account  in  considering  movements  on  our  globe,  though 
its  whole  work  consists  in  resisting  and  checking  other 
agencies. 

Force  Defined. — The  sense  of  resistance  which  our 
muscles  experience  when  we  try  to  overcome  friction,  or 
to  set  anything  in  motion,  gives  us  the  idea  of  Force. 
Any  cause  which  holds  things  together,  or  sets  things  in 
motion ',  or  alters  the  speed  or  the  direction  of  moving  things, 
is  called  a  "  Force" 


2O6  THE  FORCES  OF  NATURE. 

Perhaps  we  shall  most  easily  realize  the  immense  and 
constant  work  of  some  of  these  forces  by  thinking  what 
the  world  would  be  like  without  them.  There  is  a  charm- 
ing fairy-tale  called  "  The  Light  Princess,"  in  which  that 
unfortunate  young  lady  is  deprived  of  her  gravity,  in 
more  senses  than  one,  and  therefore  habitually  floats 
about  the  ceilings  instead  of  remaining  on  the  ground, 
and  when  out  of-doors  has  to  be  carefully  anchored.  If 
gravity  disappeared  altogether,  not  only  should  we 
follow  her  example,  but  so  would  our  furniture,  houses, 
and  everything  in  the  world,  and  that  without  the 
possibility  of  being  anchored,  while  the  world  itself 
would  say  good-bye  to  the  sun,  and  depart,  cold  and 
dark,  into  space. 

Quite  as  disastrous  would  be  a  state  of  things  without 
cohesion.  If  nothing  ever  held  together,  but  all 
crumbled  down  to  its  smallest  particles,  the  only  ques- 
tion would  be  whether  the  world  would  remain  as  a 
huge  dustheap,  or  whether  it  would  not  rather  all  fly 
away  in  a  mixture  of  gases. 

If,  however,  we  had  only  to  dispense  with  friction, 
we  might  indeed  still  have  a  world,  but  a  world  very 
like  a  bad  dream,  in  which  we  were  for  ever  trying  to 
balance  ourselves  on  surfaces  smoother  than  ice,  and 
to  lay  hold  of  things  more  slippery  than  eels. 


CHAPTER   XII. 


WE  must  now  try  to  understand  exactly  what  is  meant 
by  the  words  Work  and  Energy.  Work  means  ttie  over- 
coming through  any  distance,  any  kind  of  resistance.  The 
greater  the  distance  moved  through  or  the  resistance 
overcome,  the  greater  is  the  work  done.  Now  the  name 
"  Energy  "  is  given  to  the  power  of  overcoming  resistance. 
Hence  energy  is  the  capacity  for  doing  work.  It  implies, 
therefore,  not  only  a  Force  but  a  Space,  through  which  the 
force  is  free  to  act.  An  illustration  will  make  this  clear. 
Let  us  suppose  you  pick  up  a  heavy  ball — say  a  croquet 
ball — and  carry  it  up  to  the  top  of  a  church  tower. 
As  long  as  it  lay  still  upon  the  ground,  the  force  of 
gravity  was  not  causing  any  motion ;  it  was  apparently 
inert;  but,  by  taking  the  ball  further  away  from  the 
centre  of  the  earth,  we  have  given  the  force  space  through 
which  to  act,  and  now  it  can  produce  vigorous  motion.  At 
the  top  of  the  tower  you  must  hold  the  ball  fast,  or  it 
will  be  off,  to  a  certainty.  It  now  has  energy ;  but  your 
superior  strength  prevents  it  from  obeying  the  downward 
pull,  and  so  the  energy  remains  stored  up  in  the  ball, 
waiting  till  it  has  a  chance  of  acting.  Energy  stored  up 


208  THE  FORCES  OF  NATURE. 

like  this,  waiting   for  its  opportunity,  is  called  Energy 
of  position  or  Potential  Energy. 

If  you  presently  let  go  and  allow  the  ball  to  fall,  the 
gravitation  will  not  only  desire  to  draw  it  to  the  earth  but 
will  actually  do  it — as  it  falls  the  ball  loses  the  energy  of 
position  given  to  it  and  gains  energy  of  motion ;  it  now 
has  active  or  Kinetic  Energy,  as  it  is  called.  Any  unfor- 
tunate person  below  who  gets  the  ball  on  his  head,  or 
who  sees  it  coming  and  jumps  out  of  the  way,  will  have 
a  very  vivid  impression  of  the  active  energy  which  it 
possesses. 

But,  perhaps,  instead  of  coming  to  the  ground,  the  ball 
may  be  caught  in  a  tree  on  the  way.  What  happens  then  ? 
The  downward  pull  is  not  exhausted,  but  the  action 
is  stopped ;  the  ball  still  has  some  energy  of  position, 
which  will  become  energy  of  motion  as  soon  as  the  ball 
is  set  free  to  move  on.  When,  however,  the  fall  is  over, 
and  the  ball  and  earth  are  together,  the  gravitation 
tendency  is  so  far  satisfied  and  is  no  longer  active  ;  there 
is  no  activity  left  in  the  ball,  its  energy  is  gone  some- 
where else.  But  does  the  gravitation  force  cease  ?  No, 
but  its  effect  is  different;  it  does  not  now  produce 
motion,  but  it  holds  the  ball  and  earth  together,  offering 
quiet  resistance  to  the  attempts  of  other  forces  to 
separate  them.  It  is  as  if  the  force  between  the  two, 
being  satisfied,  went  to  sleep ;  but  it  is  there,  and  would 
be  instantly  awakened  by  any  attempt  to  lift  the  ball. 

Therefore  things  only  possess  potential  energy  when 
they  have  some  position  of  advantage  towards  something 
else,  and  things  only  possess  kinetic  energy  when  they 
have  some  kind  of  motion,  visible  or  invisible.  If  we 


POTENTIAL  ENERGY.  2CX) 

want  to  give  fresh  energy  to  the  ball  after  it  has  fallen 
to  the  ground,  we  can  do  so  by  sending  it  flying  with  a 
kick,  or  by  lifting  it  up  once  more ;  but  in  either  case  we 
must  give  up  just  as  much  of  our  own  energy  as  the  ball 
gets.  When  you  carry  the  ball  up  the  tower,  at  every  step 
of  the  way  you  are  spending  energy,  part  of  which  is  pass- 
ing into  the  ball,  and  all  the  energy  to  fall  which  it  pos- 
sesses when  the  top  is  reached  is  taken  from  you.  In 
ascending  the  tower  your  muscles  have  been  at  work,  and 
the  muscular  energy  which  you  have  thus  been  expending 
has  necessarily  been  increased  by  the  weight  of  the  ball 
you  have  carried.  Thus  the  raised  or  kicked  ball  derives 
its  energy  from  the  store  you  possessed,  and  this  store 
was  in  its  turn  derived  from  the  food  you  have  digested. 
Just  in  the  same  way,  when  water  is  pumped  up  into 
raised  tanks,  the  muscular  or  other  power  that  is  used 
in  working  the  pump  gives  away  to  the  water  just  as 
much  of  its  own  energy  as  the  water  will  use  in  flowing 
down  again ;  and  as  long  as  the  water  remains  in  the 
tank  the  energy  is  stored  up  in  it  as  potential  energy. 
Or,  if  we  stop  water  that  is  naturally  flowing  downwards, 
and  so  already  possesses  energy,  by  building  a  dam 
across  the  stream,  the  gravitation  tendency,  thus  stopped 
in  the  middle  of  its  action,  is  stored  up  in  the  water  as 
potential  energy.  In  either  case  the  water  will  certainly 
flow  down  again  at  the  first  opportunity,  spending  its 
energy  as  it  does  so ;  and  by  regulating  its  opportunities 
for  flowing,  we  can  settle  what  the  energy  shall  pass 
into  as  it  leaves  the  water.  If  a  water-wheel  is  placed  in 
its  path,  some  of  the  energy  will  pass  into  this,  and  can 
be  set  to  grinding  corn  or  sawing  wood  ;  while  the  water, 


210  THE  FORCES  OF  NATURE. 

when  it  lias  reached  its  lowest  possible  point,  conies  to 
rest — no  more  work  can  be  had  out  of  it  until  something 
energetic  comes  and  raises  it  up  again. 

When  a  coal  fire  burns  and  gives  out  heat,  there  is  a 
great  deal  of  very  active  energy  at  work.  Where  does 
it  come  from  ?  It  comes  out  of  another  unsatisfied  force, 
the  chemical  attraction  which  exists  between  oxygen  and 
coal,  or  rather  the  substance  called  carbon  in  the  coal. 
While  coal  and  oxygen  are  both  cold  they  have  no 
opportunity  of  combining ;  the  force  is  prevented  from 
acting,  and  so  is  stored  up  in  the  fuel  as  potential  energy. 
But  when  the  coal  is  sufficiently  heated  by  putting  burning 
sticks  under  it,  it  begins  to  combine  with  the  oxygen  in 
the  air. 

From  what  we  have  said  it  is  quite  clear  that  when 
you  turn  on  a  water-tap  and  set  the  water  running,  you 
do  not  thereby  give  the  energy  to  the  water ;  all  you  have 
done  is  to  set  going  the  change  from  the  energy  of 
position  which  the  water  possessed  to  energy  of  motion. 
In  the  same  way  if  a  ball  is  caught  in  a  tree,  or  a  stone 
on  the  roof  of  a  house,  and  some  one  dislodges  either, 
they  have  simply  set  free  the  stored  energy  which  the 
ball  or  stone  may  have  had  for  years  undisturbed  and 
undiminished.  And  so  the  person  who  lights  a  fire  does 
not  have  to  supply  the  energy  used  in  the  burning, 
because  the  fuel,  being  full  of  stored  energy,  only  needs 
just  so  much  additional  help  as  will  suffice  to  remove 
the  obstacle  which  prevented  the  chemical  affinity  from 
acting.  Thus  the  potential  energy  of  the  fuel  is  changed 
into  the  active  energy  of  Heat,  and  in  this  form  it  can 
be  set  to  fresh  tasks,  or  converted  again  to  other  forms 


TRANSFORMATIONS  OF  ENERGY.  211 

of  energy.  If  the  fire  is  made  under  the  boiler  of  a 
steam  engine  the  heat  will  set  the  engine  to  work ;  if  it 
is  beside  the  kitchen  oven  it  will  cook  our  food,  the 
energy  passing  again  as  it  does  so  into  another  phase  of 
chemical  affinity,  and  bringing  about  chemical  changes  in 
the  food. 

We  can  easily  put  together  long  series  of  transforma- 
tions of  energy.  First,  potential  energy  in  cold  fuel 
waiting  to  combine  with  oxygen,  then  the  same  getting 
its  opportunity  and  changing  into  active  energy  as  heat 
under  a  boiler;  the  heat  gives  away  its  energy  to  the 
water,  heating  it  into  steam ;  the  steam  works  a  pumping 
engine,  and  at  every  stroke  gives  away  energy  to  the 
pumped-up  water,  in  which  it  is  perhaps  stored  away 
again  for  a  time  as  the  potential  energy  of  unsatisfied 
gravitation.  But  when  the  water  is  allowed  to  flow  and 
the  energy  becomes  active  again,  it  may  be  paid  away 
in  turning  a  water-wheel,  and  if  the  wheel  is  employed  to 
drive  an  electric  machine  we  may  presently  see  the 
energy  reappear  in  the  brilliant  form  of  the  electric  light. 

So  energy  runs  round  and  round,  acting  now  in  this 
force  and  now  in  that,  moving  things  from  their  places, 
or  altering  their  shape  and  condition,  making  cold  things 
hotter,  or  melting  solid  substances  into  liquids,  or  com- 
bining them  chemically  into  new  substances,  or  pro- 
ducing the  activities  of  light,  sound,  electricity,  etc. 
Only  in  the  very  act  of  performing  each  of  these  works, 
it  is  passing  away  into  some  other  form.  For  the 
energy  is  not  destroyed,  it  is  not  dead  and  gone ;  it  does 
but  pass  off  to  other  forms  of  activity,  or  else  is  stored 
up  waiting  for  its  next  opportunity. 


212  TlfE  FORCES  OF  NATURE. 

A  good  illustration  of  the  whole  subject  is  found  in 
its  likeness  to  the  use  of  money.  As  long  as  our 
money  is  stored  up  in  the  bank  it  is  in  the  condition 
of  potential  energy.  It  is  at  our  command.  We  have 
the  power  to  use  it  as  we  please,  but  we  are  not  at  the 
moment  using  it.  When  we  pay  money  away  for  any- 
thing, it  is  gone,  so  far  as  we  are  concerned.  We  have 
had  our  money's  worth  in  the  goods  which  we  have 
bought,  just  as  we  had  the  worth  of  the  energy  in  the 
work  which  it  has  accomplished.  The  money  is  gone 
from  us ;  we  cannot  use  it  again.  But  it  has  not 
perished.  The  person  to  whom  we  paid  it  has  it  now, 
and  it  may  either  be  stored  up  again  by  him,  or  paid 
away  to  a  third  person  for  some  other  goods,  and  so 
keep  on  circulating.  And  the  money  may  be  in  dif- 
ferent shapes — now  in  cheques,  now  gold,  now  silver, 
now  English  money,  now  foreign,  but  always  represent- 
ing the  same  value,  and  having  the  same  purchasing 
power. 

Fresh  money  may  indeed  be  coined  from  time  to 
time,  but  we  cannot  ever  coin  fresh  energy ;  whatever 
energy  is  used  must  be  obtained  from  something  that 
already  has  it,  and  so  it,  like  the  money,  is  kept 
circulating. 

An  experiment  may  help  us  to  understand  better  the 
constant  change  from  energy  of  position  to  energy  of 
motion,  or  vice  versfr,  which  is  always  going  on  around 
us.  Tie  a  small  but  rather  heavy  weight  to  the  end  of 
a  string,  and  hang  it  up  so  that  the  string  and  the  weight 
can  swing  freely.  Then,  if  you  move  the  weight  up  into 
the  position  of  A  (p.  213),  and  there  let  it  go,  it  will 


ALTERNATING    TYPES  OF  ENERGY.          213 

be  at  once  drawn  down  again  by  gravitation.  The  string 
will  not  allow  it  to  fall  straight  down,  so  that  it  falls  in 
the  only  direction  it  can,  back  towards  B.  When  it 
reaches  B,  the  lowest  An 

place  possible  to  it, 
the  gravitation  moves 
it  no  longer ;  but  the  / 

weight  is  full  of  energy,  / 
and  as  there  is  nothing  ••''[ 
to  stop  its  motion,  it  ^ 
continues  to  move  in 
the  same  direction  un- 
til it  has  swung  up  to  C, 
as  high  as  it  was  at  A.  By  this  time  its  energy  of  motion 
is  used  up ;  but  it  has  gained  energy  of  position,  for  the 
weight  is  now  in  such  a  position  that  it  can  again  acquire 
active  energy  from  gravitation,  so  that  it  is  drawn  back 
to  B,  acquiring  on  the  way  momentum  which  carries  it 
up  again  towards  A,  and  so  the  swing  goes  on. 

If  there  were  no  resistance  it  would  go  on  for  ever, 
or,  at  least,  until  the  string,  and  that  which  the  string 
hangs  from,  were  worn  out.  But  as  in  every  swing  a 
little  of  the  energy  is  taken  up  in  overcoming  the  resist- 
ance of  the  air,  the  weight  never  really  rises  quite  up  to 
the  same  height  again,  and  so  getting  lower  and  lower 
each  time,  gradually  comes  to  rest  at  the  bottom  point  B. 
When  we  wind  up  a  clock  our  muscles  supply  the  energy, 
which  is  stored  in  the  coiled  spring  or  raised  weights  of 
the  clock,  and  this  stored  energy  is  drawn  upon  to  over- 
come friction  and  keep  the  pendulum  always  swinging, 
and  the  wheel-work  moving. 


214  THE  FORCES  OF  NATURE. 


CHAPTER   XIII. 

WEIGHT   AND    DENSITY. 

IF  you  were  standing  by  a  church  tower,  and  some  one 
threw  down  from  the  top  a  cork  which  fell  on  your  head, 
you  would  get  a  sharp  tap  from  it,  but  you  would  not  be 
injured;  if,  however,  a  stone  of  the  same  size  were  dropped 
on  your  head  there  would  be  a  very  different  tale  to  tell. 
What  makes  so  much  difference  between  the  stone  and 
the  cork  ?  We  say  that  the  stone  is  heavier ;  it  has 
more  matter — and  therefore  more  active  energy  at  the 
end  of  its  fall — than  the  piece  of  cork. 

Do  you  remember  that  when  the  fallen  picture  was 
lifted  up,  we  found  that  the  weight  of  it  meant  the 
measure  of  its  resistance  to  being  separated  from  the 
ground ;  that  is,  of  the  attraction  which  the  earth  has 
for  it  ?  So,  if  the  stone  is  heavier  than  the  cork,  it  must 
mean  that  it  is  more  strongly  attracted  to  the  earth  than 
the  cork.  Take  a  large  lump  of  cork  in  your  right  hand, 
and  a  stone  the  same  size  in  the  left,  and  hold  them  up 
side  by  side ;  you  will  find  the  stone  pressing  heavily 
down  towards  the  ground,  and  will  have  to  use  much 
more  strength  to  keep  the  left  hand  from  sinking  than 
the  right.  The  gravitation  tendency,  then,  is  stronger 
in  some  things  than  in  others ;  or,  to  put  it  more  simply, 
some  things  are  heavier,  bulk  for  bulk,  than  others. 


THE    VELOCITY  OF  FALLING  BODIES.       21$ 


But  though  the  strength  of  attraction,  or  the  weight, 
may  be  different,  yet  the  pace  at  which  things  fall,  their 
velocity,  as  it  is  called,  is  the  same  for  all  things  falling 
from  the  same  height,  unless  some- 
thing gets  in  the  way  and  resists 
one  fall  more  than  another.  This 
seems  a  strange  thing  to  say,  and 
we  may  very  likely  think  that  it 
cannot  be  true.  What?  Is  it 
meant  that  if  a  stone  and  a  cork 
and  a  handkerchief  and  a  feather 
were  all  dropped  from  the  top  of 
the  tower  together  they  would  all 
reach  the  ground  at  the  same  time  ? 
No,  certainly  not ;  the  stone  would 
come  down  first ;  but  then  we  have 
to  consider  what  they  fall  through. 
They  pass  through  the  air,  and  the 
lighter  bodies,  in  falling,  have  less 
energy  to  overcome  the  resistance 
of  the  air  in  proportion  to  their 
surfaces.  It  can  be  proved  that 
any  difference  in  their  velocity  is 
due  to  the  surrounding  air,  for  when 
they  are  made  to  fall  in  a  place 

from   which    all   air   is    pumped    OUt,      Coin  and  Feather  falling 

then   it   is   found   that   all   bodies, 

whatever  their  weight,  will  reach  the  bottom  in  exactly 

the  same  time. 

Here  is  a  picture  of  a  glass  tube,  g,  about  six  feet  long, 
closed  at  one  end,  and  having  a  stop-cock  at  the  other, 


2l6  THE  FORCES  OF  NATURE. 

and  containing  a  coin,  c,  and  a  feather,  /, — any  small 
objects  will  do.  By  connecting  the  tube  with  an  air- 
pump  all  the  air  can  be  sucked  out  of  it,  and  if  the  cock 
is  then  closed,  and  the  tube  suddenly  turned  upside  down, 
all  the  objects  contained  in  it  will  fall  to  the  other  end 
in  the  same  time.  The  hands  are  held  in  the  way 
shown,  so  that  the  tube  can  be  quickly  inverted. 

But  now  we  come  to  another  point.  Instead  of 
travelling  all  the  way  down  at  an  even  pace,  each  thing 
begins  to  fall  comparatively  gently,  and  gets  faster  and 
faster  all  the  way  down,  so  that  the  further  it  falls  the 
greater  becomes  its  speed.  You  may  see  something  of 
this  difference  in  water  falling  from  a  height.  Get  some 
one  to  pour  water  from  a  kettle  out  of  the  first  floor 
window,  and  look  at  the  falling  water.  The  top  of  it 
where  it  leaves  the  spout  is  a  gentle  continuous  stream, 
but  a  little  below  it  becomes  hurried  and  uneven  in  its 
flow,  and  presently,  as  it  gets  faster  and  faster,  breaks 
apart  into  separate  drops. 

The  reason  for  this  quickening  of  speed  is  curious  and 
interesting. 

We  notice  in  the  things  round  us  that  not  only  do 
bodies  at  rest  remain  motionless  until  some  force  sets 
them  moving ;  but  bodies  once  set  in  motion  go  on  and 
on  until  some  force  stops  them.  The  main  stopping 
force  on  the  surface  of  the  world  is  friction  ;  but  our 
world  itself  and  the  stars,  as  there  is  no  friction  to  inter- 
fere with  them,  roll  on  and  on  in  their  paths  because 
nothing  stops  them.  Well,  then,  when  a  stone  leaves  the 
hand  of  a  person  on  the  top  of  the  tower,  the  force  of 
gravity  starts  it  moving  towards  the  earth  :  but  if  the 


MOMENTUM.  2  1 7 

gravitation  force  left  off  acting  the  instant  after,  and  had 
no  more  effect  upon  the  stone,  it  would  still  move  steadily 
on  because,  having  once  been  set  going,  go  it  must, 
straight  on  in  the  same  direction,  until  something  turns 
or  stops  it.  Instead  of  that,  however,  the  force  of 
gravity  keeps  on  urging  it  afresh  every  moment  of  its 
fall,  giving,  as  it  were,  fresh  and  fresh  pulls  beyond  what 
is  needed  to  bring  it  down ;  so  all  this  added  force  goes 
to  make  it  travel  faster  and  faster,  and  the  further  it  falls 
the  greater  becomes  the  velocity  or  pace  of  its  falling. 

It  is  usual  to  measure  the  velocity  of  a  moving  body 
by  the  number  of  feet  it  travels  in  a  second,  while  the 
weight  of  it  is  measured  in  pounds.  So  if  we  have  a  ball 
weighing  five  pounds  moving  at  the  rate  of  ten  feet  a 
second,  we  should  say  its  weight  is  five  and  its  velocity 
is  ten ;  and  by  multiplying  the  weight  and  velocity 
together  we  find  what  is  called  the  momentum,  which  in 
this  case  would  of  course  be  fifty.  An  iron  ball  has  more 
momentum  than  a  wooden  ball  of  similar  size  dropped 
from  the  same  height,  because  its  mass  is  greater.* 

Now,  when  the  motion  suddenly  comes  to  an  end — 
when  the  falling  body  reaches  the  ground,  or  the  bullet 
strikes  something — what  becomes  of  all  its  energy  ?  Well, 
it  will  do  some  work  or  other ;  but  what  the  particular 
effect  will  be  depends  on  the  amount  of  its  energy  and 
the  condition  of  the  surface  against  which  it  strikes. 
If  a  heavy  body  has  fallen  a  great  distance,  so  that 
its  energy  is  great,  it  is  not  unlikely  to  use  its  energy 

*  "  Mass  "  is  "  quantity  of  matter,"  and  is  everywhere  a  constant 
property  of  a  body,  whereas  the  weight  of  a  body  varies  with  the 
force  of  gravitation. 


2l8  THE  FORCES  OF  NATURE. 

in  burying  itself  in  the  ground,  or  in  ploughing  it  up. 
If  it  falls  into  water,  the  water  will  be  set  in  violent 
motion,  splashing  out  and  heaving  and  rippling  in  all 
directions.  If  a  hard  body  falls  on  a  hard  unyielding 
surface  the  energy  will  turn  to  heat  and  make  them  both 
hot ;  while  an  elastic  body  will  probably  spend  its  energy 
in  bounding  up  again. 

Density  and  Volume. — Have  you  ever  seen  an  old 
wool  mattress,  thin  and  hard  with  long  wear,  unpicked 
to  have  its  stuffing  put  right  again  ?  Out  comes  the 
stuffing,  squeezed  into  hard  flat  lumps  and  wisps,  and 
then  the  pickers  set  to  work  and  pull  asunder  every  lock 
and  curl  of  the  wool  till  all  is  light  and  soft  as  a  snow- 
drift. But  how  much  room  it  takes  now  !  As  it  came 
out  there  was  not  even  enough  to  fill  the  old  mattress 
bag,  and  now  it  has  become  a  mountain  of  wool  several 
feet  high.  Is  it  really  the  same  quantity ;  and  how  can 
we  measure  quantities  which  vary  so  much  in  size  and 
appearance?  Well,  one  thing  has  remained  the  same 
throughout,  and  that  is  its  weight ;  so  that  by  weighing 
it  before  and  after  picking  we  can  make  sure  that  the 
quantity  of  matter,  or  mass,  as  we  call  it,  is  the  same. 

Our  mountain  of  wool  illustrates  for  us  the  three  things 
that  we  must  learn  to  observe  in  every  substance  that  we 
have  to  deal  with.  First,  its  mass,  which  is  a  constant 
quantity ;  secondly,  the  space  which  it  fills,  called  the  size, 
or  volume,  or  bulk  ;  and  thirdly,  the  closeness  with  which 
the  particles  are  packed  together,  or  the  density.  The 
quantity  of  wool  being  always  the  same,  the  volume  and 
the  density  vary  together,  but  in  opposite  ways,  or  in- 
versely; that  is,  when  the  wool  occupies  the  largest  space, 


THE  DENSITY  OF  OBJECTS.  219 

it  is  most  loosely  packed,  it  is  least  dense ;  when  the 
packing  becomes  denser,  the  size  or  volume  becomes  less. 

When  solid  and  liquid  substances  change  their  density 
and  volume  it  is  generally  through  being  heated  or 
cooled,  since  heat  lessens  the  cohesion,  so  that  the 
particles  are  not  held  so  closely  together,  making  the 
density  less  and  the  volume  greater.  But  we  are  all 
well  aware  in  everyday  life  that,  even  when  equally  cool, 
different  substances  have  very  different  densities.  Look 
at  the  grocer  weighing  a  pound  of  butter.  How  much 
larger  the  pound  of  butter  is  than  the  pound  weight  in 
the  other  scale  !  That  is  because  butter  is  less  dense 
than  the  metal,  so  that  a  larger  bulk  of  it  goes  to  make 
up  the  same  weight ;  and  a  pound  of  isinglass  would  be 
much  larger  again  because  its  density  is  much  less. 

Specific  Gravity. — It  is  not  enough  to  say  greater  or 
less;  we  often  require  to  know  how  much  greater  and 
how  much  less,  and  for  these  comparisons  of  density  it 
is  the  custom  to  weigh  things  against  water,  which  makes 
a  convenient  standard.  We  have  to  take  an  equal  bulk 
of  the  thing  to  be  tested,  say  a  marble,  and  of  pure 
water  and  to  weigh  them  both ;  if  we  then  divide  the 
former  weight  by  the  latter,  we  get  the  specific  weight  or 
specific  gravity  of  the  marble,  that  is  the  number  of 
times  it  is  heavier  than  water. 

But  how  shall  we  be  sure  what  bulk  of  water  is  equal 
to  the  bulk  of  what  we  have  to  weigh  ?  In  the  case  of 
liquids  this  can  be  found  out  by  first  pouring  water  into 
a  glass  vessel  up  to  a  fixed  mark  and  weighing  it ; 
then  after  emptying  and  carefully  drying  the  glass,  fill  it 
up  to  the  same  height  with  the  other  liquid  and  weigh 


220  THE  FORCES  OF  NATURE. 

again.  The  glass  being  the  same  in  both  cases,  the 
difference  in  the  weights  will  be  caused  entirely  by  the 
different  densities  of  the  liquids.  With  solids  we  must 
use  a  rather  different  plan.  Suppose  we  have  a  small 
glass  ball  to  test.  Let  us  pour  water  into  our  measured 
glass  up  to  the  line  marked,  say,  thirty,  and  then  drop  in 
the  glass  ball.  The  water,  of  course,  will  rise  higher,  and 
if  we  find  that  it  rises  to  forty,  then  it  is  plain  that  the 
bulk  of  the  ball  is  equal  to  a  bulk  of  water  that  fills  ten 
divisions.  If  the  ball  weighs  6  ounces  and  the  ten  divi- 
sions of  water  weigh  2  ounces,  then  the  specific  gravity 
of  the  ball  is  6  -r-  2  =  3  ;  that  is,  it  is  three  times  heavier 
than  the  same  bulk  of  water.  This  method  answers  well 
for  small  solid  things  that  do  not  dissolve  in  water. 

For  the  reason  given  below,  any  substance  weighed 
in  water  appears  less  heavy  than  when  it  is  weighed  in 
the  air.  Let  a  solid  substance,  say  one  of  the  larger 
metal  weights,  be  put  into  one  scale  of  a  balance,  and 
weights  be  added  in  the  other  scale  until  it  is  exactly 
balanced;  we  have  then  found  its  weight  in  the  air. 
Then  hanging  it  on  to  a  hook  below  the  scale,  place  a 
jar  under  it  and  pour  in  water  until  the  whole  of  the 
weight  is  under  water.  We  shall  find  that  the  balance 
is  no  longer  even ;  the  water  gives  more  support  to  the 
weight  than  the  air  did,  so  that  the  other  scale  is  now 
become  too  heavy.  By  taking  off  weights  from  the  other 
side  until  the  two  are  again  exactly  balanced,  we  can 
ascertain  how  much  weight  has  been  lost  by  weighing  in 
water ;  and  we  shall  find  in  every  case  that  anything 
weighed  in  water  loses  just  the  weight  of  a  quantity  ofwatei- 
equal  to  its  oii'ti  bulk. 


SPECIFIC  GRAVITY.  221 

If  we  now  detach  the  metal  weight  and  let  it  go,  it 
will,  of  course,  drop  down  to  the  bottom  of  the  water, 
for,  though  it  lost  part  of  its  weight,  yet  it  is  so  much 
heavier  than  water  that  there  is  plenty  left  to  make  it 
sink.  If,  however,  the  experiment  were  tried  with  some- 
thing exactly  the  same  density  as  water,  then,  on  being 
detached,  it  would  remain  where  it  was  in  the  middle 
of  the  water,  neither  going  up  nor  down.  A  substance 
lighter  than  water  cannot  be  weighed  alone  in  water,  as 
it  will  rise  up  towards  the  surface  and  float.  If  it  is 
half  the  density  of  water,  it  will  rise  till  half  of  it  is  above 
the  surface ;  if  only  a  quarter  the  weight,  three-quarters 
of  it  will  rise  out  of  the  water.  To  find  what  such  a 
substance  loses  in  weight  when  immersed,  we  must,  after 
weighing  it  in  the  air,  load  it  with  something  heavier 
whose  weight  in  air  and  water  has  been  ascertained,  and 
then,  weighing  them  in  water,  subtract  the  loss  in  weight 
of  the  heavy  body  alone  from  the  loss  in  weight  of  the 
two  together. 

Comparing  in  these  ways  the  densities  of  different 
substances,  we  find  that  a  certain  kind  of  glass  is  2\ 
times  as  heavy  as  water:  then  2\  (or  2^5)  is  called  the 
specific  gravity,  or  sometimes  the  density,  of  that  glass, 
the  weight  of  pure  ice-cold  water  being  taken  as  unity, 
i.e.  i .  Heavy  flint  glass  has  a  greater  specific  gravity,  and 
is  3^-  times  the  weight  of  water.  The  specific  gravity 
of  coal  is  i '3,  of  iron  7 '8,  of  lead  n-4.  Among  things 
lighter  than  water,  the  specific  gravity  of  wood  varies 
in  different  kinds  from  four-fifths  to  two-fifths  the  weight 
of  water,  while  cork  is  about  one-fourth,  or  0-25. 

As  yet  we  have  been  speaking  only  of  solid  lumps  of 


222  THE  FORCES  OF  NATURE. 

substance,  the  same  all  the  way  through,  and  when  this 
is  the  case  we  have  only  the  specific  gravity  to  consider, 
so  that  anything  with  greater  specific  gravity  than  water 
will  sink,  or  with  less  specific  gravity  will  float. 

But  now  take  a  hollow  ball  of  thin  sheet  copper. 
If  all  the  copper  it  contains  were  hammered  down  into 
a  solid  lump  it  would  make  but  a  very  small  ball, 
and  would  be  much  heavier  than  a  ball  of  water  the 
same  size,  but  when  beaten  out  thin  and  shaped  so 
as  to  enclose  a  large  quantity  of  air,  then  the  ball  with 
the  air  it  contains  is  lighter  than  a  ball  of  water  the 
same  size — lighter,  as  we  say,  bulk  for  bulk,  and  so  it 
will  float  in  water.  This  is  what  makes  it  possible  to 
build  ships  of  so  heavy  a  material  as  iron.  Were  the 
iron  a  solid  lump  it  would  go  to  the  bottom  at  once, 
but  the  iron  shell  of  the  vessel  is  made  to  enclose 
so  large  a  space  that  it  displaces  a  great  deal  of  water, 
and  hence  the  vessel,  with  all  its  fittings  and  cargo  and 
crew,  still  is  lighter,  bulk  for  bulk,  than  water,  and  so 
will  float. 


CHAPTER   XIV. 

PRESSURE   OF    FLUIDS.      THE    BAROMETER. 

Pressure  of  Liquids. — If  we  have  a  square  box  con- 
taining a  block  of  wood  which  exactly  fills  it  up,  the 
sides  as  well  as  the  bottom  being  everywhere  in  contact, 
and  then  by  means  of  a  cover  and  handle,  bring 
strong  pressure  down  upon  the  top  of  it,  we  shall 
make  the  wood  press  more  heavily  and  closely  against 
the  bottom  of  the  box,  but  the  pressure  will  make 
no  difference  at  all  to  the  sides.  The  sides  might  be 
replaced  by  the  thinnest  tissue  paper,  but  it  would  not 
bulge  or  be  torn,  for  the  pressure  all  goes  downwards. 
If,  however,  the  wood  were  taken  out,  and  the  box  filled 
up  with  water  instead,  the  case  would  be  quite  different. 
Then,  any  pressure  made  upon  it  would  press  as  heavily 
against  the  sides  as  against  the  bottom,  and  if  the  sides 
were  replaced  by  any  thin  weak  material  they  would 
burst  asunder  :  for  in  liquids  pressure  is  communicated 
equally  in  all  directions,  sideways  and  upwards,  as  well 
as  downwards. 

To  see  the  upward  pressure  of  water,  take  any  open 
tube — a  common  lamp  chimney  does  very  well — and 
close  its  lower  end  with  a  card,  which  can  be  held  in 
place  for  the  moment  by  a  thread  tied  to  it  and  carried 


224  TIIE  FORCES  OF  NATURE. 

up  through  the  tube.  Plunge  the  tube  thus  closed  into  a 
vessel  of  water,  and  you  may  let  the  thread  go,  for  the 
card  will  be  firmly  held  in  its  place  by  the  pressure 
upward  of  the  water  against  it. 

When  the  pressure,  instead  of  being  made  from  outside, 
is  caused  by  the  mere  weight  of  the  water  itself  pressing 
on  its  own  lower  layers,  it,  of  course,  increases  with  the 
depth  of  the  water.  You  know  that  if  the  tap  of  the 
water-butt  is  opened  when  the 
butt  is  full,  the  pressure  of  all 
the  water  above  not  only  forces 
water  out  of  the  tap,  but  gives 
it  so  much  momentum  that  the 
stream  spurts  out  in  a  horizontal 
direction  for  a  short  distance 
before  gravity  draws  it  down  to 
B  '  ""*"  the  ground  (as  at  A  in  the  picture). 

Water  spouting  from  butt.         £ut  wnen  t}ie  butt  jg  on}y  najf  fyjj^ 

the  water  has  less  momentum  from  pressure,  and  reaches 
the  ground  in  a  much  shorter  curve,  B  ;  while,  when  it 
is  nearly  empty,  there  is  a  mere  trickle  from  the  tap, 
with  no  spurting  power  left  in  it. 

We  have  seen  that  the  top  of  any  liquid,  when  at  rest, 
is  always  a  level  surface,  and  this  is  true  not  only  when 
it  is  all  contained  in  one  vessel,  but  in  any  number  of 
vessels  of  any  shape  or  size,  provided  they  all  com- 
municate with  each  other  below.  Thus  the  water  always 
stands  at  the  same  level  in  a  watering-pot  and  its 
spout.  The  watering-pot  is  like  a  large  tube,  and  the 
spout,  a  small  one,  opening  into  each  other  below ;  and 
you  cannot  raise  the  height  of  the  water  in  one  without 


PRESSURE  OF  GASES.  22$ 

raising  it  in  the  other  also.  Of  course,  if  one  of  the 
tubes  is  lowered  until  it  is  below  the  level  of  the  water 
in  the  other  the  water  will  run  out  until  both  stand  again 
at  the  same  level.  This  is  almost  too  obvious  to  need 
saying,  since  every  cup  of  tea  is  filled  by  the  simple 
process  of  lowering  the  spout  of  the  teapot  until  it  is 
below  the  level  of  the  tea  in  the  pot.  But  we  may  not 
have  noticed  the  same  thing  happening  on  a  larger  scale. 
A  tank  of  water  at  the  top  of  the  house,  with  a  pipe 
leading  down  from  it  to  the  garden,  and  there  turned 
upwards  again,  form  together  just  such  a  vessel  as  the 


Uniform  level  of  water  in  can  and  spout. 

teapot  with  its  spout  lowered;  and,  in  this  case,  not 
only  will  the  water  overflow  at  the  end  of  the  pipe,  but 
the  pressure  of  the  water  above  will  give  it  so  much 
momentum  that  it  will  spring  up  in  a  fountain. 

Pressure  of  Gases. — Air  has  weight.  If  it  were  not 
acted  on  at  all  by  gravitation,  then,  since  the  molecules 
of  gases  are  always  repelling  each  other,  the  air  would 
presently  fly  away  from  the  earth  altogether,  and  go  off 
into  space ;  happily,  however,  its  attraction  to  the  earth 
is  strong  enough  to  keep  it  here.  Indeed,  the  sea  of 
air  above  us  is  so  deep  that  its  weight  causes  a  very 
considerable  pressure  upon  everything  on  the  surface  of 

Q 


226  THE   FORCES   OF  X ATI' RE. 

the  earth,  amounting  on  an  average  to  about  fifteen 
pounds  on  every  square  inch,  and  so  to  several  tons  on 
the  body  of  a  man. 

Why,  then,  do  we  not  feel  weighed  down  by  this  great 
pressure  ?  If  air  pressed  like  a  solid  substance,  down- 
wards only,  we  should  be  crushed  under  it,  but  as,  like 
a  liquid,  it  presses  equally  in  all  directions,  the  sideway 
and  upward  pressures  balance  the  downward  pressure, 
and,  among  the  balanced  forces,  we  move  as  freely  as 
a  fish  moves  through  all  the  balanced  pressures  in  water. 

When,  however,  anything  causes  a  slight  difference 
in  pressure  in  different  directions  then  we  do  feel  the 
pressure  of  the  air.  If  it  is  very  slight  we  say  there  is 
'  a  breeze,  but  if  the  inequality  becomes  greater  the 
pressure  may  increase  up  to  a  terrific  gale,  before  which 
great  trees  go  down  like  nine-pins. 

Some  gases  are  heavier  than  others.  Hydrogen  gas, 
for  instance,  is  a  good  deal  lighter  than  the  mixture  of 
gases  that  we  call  air,  and  consequently  it  will  rise  and 
float  in  the  air-sea,  as  cork  rises  and  floats  in  water ; 
and  just  as  a  copper  ball,  when  enclosing  a  sufficient 
quantity  of  air,  can  float  in  water,  so  other  materials 
may  be  arranged  to  enclose  hydrogen  enough  to  make 
the  whole  mass  lighter  than  an  equal  bulk  of  the  lower 
layers  of  air,  when  it  will  rise  and  float  in  the  atmosphere. 
Such  a  ship  of  the  air  is  called  a  balloon. 

We  employ  the  pressure  of  the  air  to  do  useful  work 
for  us  in  various  ways.  Look  at  this  picture  of  the 
inside  of  a  pump.  You  see  the  barrel  or  body  of  the 
pump,  with  a  tube  below  which  dips  down  into  the 
water,  and  a  thing  inside,  called  the  piston,  A,  which 


HOW  A   PUMP  WORKS.  227 

moves  up  and  down  as  we  move  the  pump  handle.     The 

piston  fits  quite  closely  into  the  barrel  of  the  pump  so 

that  no  air  can  pass  up  or  down  round  it,  but  it  has  in 

the  middle  a  little  door  or  valve  which  can  only  open 

upwards.      Another    valve    B, 

also   opening   upwards,   closes 

the  entrance  of  the  water  pipe 

into  the  bottom  of  the  pump 

barrel.     Suppose  now  that  the 

piston,  which  is  connected  with 

a  rod  and  handle,  is  drawn  up 

to  the  top  of  the  pump,  and  by 

moving  the  handle  we  begin  to 

press     it    downwards.      What  W_  ___  -.J|fjL  --  -_  .w 

happens?      The    space   below 

it  is  full  of  air,  and  when  the 

Diagram  of  Suction-pump. 

piston    coming   down    presses 

upon  this  air  the  enclosed  compressed  air  opens  the 
upper  valve,  shuts  the  lower,  and  so  escapes  upwards. 
When  the  piston  is  at  the  bottom  there  is  not  any  upward 
push  of  the  air  and  the  upper  valve  falls  shut,  and  as 
the  piston  is  drawn  up  again,  the  air  above  pressing  on 
the  top  of  the  valve  keeps  it  firmly  closed  so  that  none 
can  return  through  it.  The  inside  of  the  barrel  is  now 
partly  emptied  of  air,  but  it  does  not  stay  empty,  for 
first  the  air,  and  then  the  water  in  the  pipe,  rushes  in, 
pushing  open  the  lower  valve  B,  and  following  the  rising 
piston.  Why  does  the  water  rush  up  into  the  tube  as 
the  piston  rises  ?  The  surface  of  the  water,  WW,  outside 
the  tube  is  bearing  the  pressure  due  to  the  atmosphere 
above  it,  and  as  long  as  the  tube  was  also  full  of  air  the 


228  THE  FORCES   OF  NATURE. 

pressure  was  balanced,  and  the  water  remained  level. 
As  soon,  however,  as  some  of  the  air  is  withdrawn  from 
the  tube,  the  pressure  outside  is  not  balanced  and  presses 
the  water  into  the  tube  to  occupy  the  space  left  vacant. 
Another  stroke  or  two  of  the  handle  pumps  out  all  the 
air  so  that  the  water  rises  up  to  the  piston,  and  then 
when  the  piston  descends  again  it  is  water  and  not  air 
that  is  forced  through  the  upper  valve ;  lastly,  on  raising 
the  piston  the  valve  closes,  the  water  is  lifted  and  flows 
out  of  the  spout. 

We  can  see  that  if  the  barrel  of  the  pump  had  no  tube 
below  to  go  into  the  water,  but  was  all  solidly  closed 
with  materials  strong  enough  to  bear  the  pressure  of  the 
air  without  breaking,  we  could  then,  by  pumping  out  all 
the  air,  have  a  really  empty  place  inside,  a  vacuum,  as  it 
is  called. 

The  water-pump  will  work  perfectly  well  as  long  as 
the  tube  is  not  too  long,  but  if  the  distance  of  the  piston 
above  the  water  is  more  than  about  thirty-three  feet  it  will 
fail,  for  the  water  will  not  rise  so  high ;  because  a 
column  of  water  thirty-three  feet  high  has  become  heavy 
enough  to  balance  the  pressure  of  the  atmosphere,  and 
when  the  forces  are  balanced  no  more  work  can  be  done. 
It  is  therefore  plain  that  a  column  of  air,  say  a  square 
inch  across,  the  whole  height  of  the  atmosphere,  has  just 
the  same  weight  as  a  similar  column  of  water  thirty-three 
feet  high.  This  is  how  we  know  that  the  atmospheric 
weight  or  pressure  is  fifteen  pounds  on  each  square  inch 
of  surface,  for  this  is  the  weight  of  a  column  of  water  a 
square  inch  across  and  thirty-three  feet  in  height. 

With  a  heavier  liquid  than  water  it  would,  of  course, 


THE  BAROMETER. 


229 


take  a  shorter  column  to  balance  the  weight  of  the 
atmosphere,  and  mercury,  the  heaviest  liquid  known, 
balances  it  with  a  column  of  about  thirty  inches. 
We  say  -about  thirty  inches  because  there  are  variations 
in  the  pressure  of  the  air ;  if  the  pressure  of  air  is  some- 
what greater,  it  can  balance  a  rather  higher  column  of 


Construction  of  .- 


mercury,  or,  if  it  is  less,  the  mercury  balanced  by  it  will 
fall  a  little.     This  is  the  explanation  of  the  barometer.* 

*  Barometer — from  two  Greek  words  meaning  "  measure  of 
weight."  As  mercury  is  13$  times  denser  than  water,  the  height 
of  the  mercurial  barometer  is  13$  times  less  than  a  water-barometer  ; 
33  feet  or  396  inches  -r-  13$  =  30  inches  nearly. 


230  THE  FORCES   OF  NATURE. 

A  barometer  consists  of  a  glass  tube  more  than  thirty 
inches  long,  closed  at  one  end.  To  prepare  it,  mercury 
is  first  poured  into  the  tube  till  it  is  quite  full,  and  then 
the  operator,  stopping  the  open  end  with  his  finger,  as 
shown  in  this  picture  at  /,  turns  the  tube  carefuFy  upside 
down  and  dips  the  end  into  a  vessel  of  mercury,  M. 
When  he  withdraws  his  finger,  the  mercury  falls  a  little 
way,  as  at  /',  because  the  column  is  more  than  thirty 
inches  high,  but  it  stops  as  soon  as  its  weight  is  balanced 
by  the  pressure  of  the  air  on  the  mercury  in  the  open 
vessel,  and  as  the  empty  space  left  above  it  in  the  top 
of  the  tube  is  a  vacuum,  the  column  rises  and  falls  with 
every  variation  in  the  weight  of  the  air,  these  changes  of 
height  being  measured  upon  a  graduated  scale,  S.  When 
we  say  that  "  the  glass  is  high,"  or  "  the  glass  is  falling  " 
(meaning,  of  course,  the  mercury  in  the  glass),  this  shows 
that  the  pressure  of  the  air  is  greater  in  the  former 
than  in  the  latter  case,  and  as  rain  rarely  falls  when  the 
atmospheric  pressure  is  great,  the  barometer  is  given  the 
name  of  the  weather-glass. 


CHAPTER  XV. 

THREE   STATES    OF    MATTER —  COHESION. 

IF  we  take  a  good  lump  of  ice,  and  put  it  into  a 
saucepan  in  front  of  the  fire,  the  outside  of  it  will  first 
grow  moist  and  melt,  and  drip  into  the  bottom  of  the 
pan,  then  the  next  layer  will  go  in  the  same  way,  until 
the  whole  ice  is  slowly  changed  into  \vater.  The  ice 
stood  up  in  a  lump  of  uneven  shape,  reaching  above 
the  top  of  the  pan  but  not  filling  the  bottom.  The 
water,  on  the  contrary,  runs  down  and  fills  all  the 
bottom  and  sides  till  it  is  exactly  of  the  shape  of  the 
pan,  only  with  a  flat,  level,  upper  surface. 

Now,  let  us  put  our  saucepan  of  melted  ice  on  the 
fire.  The  water  gradually  becomes  hotter  and  hotter, 
and  steam  begins  to  rise  from  it  into  the  air.  Presently 
it  bubbles,  and  heaves,  and  boils,  and  throws  oft"  steam 
in  clouds ;  do  not  take  it  off  the  fire,  but  watch  what 
happens.  It  continues  to  boil,  but  there  is  less  and  less 
of  it  in  the  pan,  and  if  allowed  to  remain  over  the  fire 
every  drop  will  disappear,  and  the  pan  be  quite  empty 
and  dry.  What  becomes  of  the  water  ?  Where  is  it 
gone  ?  It  is  all  changed  into  vapour,  and  as  such  gone 
away  into  the  air. 

If  instead  of  boiling  it  in  an  open  saucepan,  we  put  it 


232  THE  FORCES   OF  NATURE, 

into  a  kettle  with  a  tightly  closed  lid,  the  steam  and 
vapour  will  pour  out  of  the  spout.  Let  us  lengthen  the 
spout  by  fixing  to  the  end  of  it  a  good  long  tube,  as  in 
the  picture,  and  wrap  round  the  tube  a  cloth  wrung  out  of 
cold  water.  This  cools  the  vapour  on  its  way  through 
the  tube,  and  as  it  loses  its  heat  it  is  condensed,  that  is, 
it  changes  back  again  into  water,  which  drips  from  the 
end  of  the  tube  into  the  basin  set  underneath.  We  shall 
have  to  keep  on  cooling  the  wet  cloth  as  it  gets  warm, 
and  gradually  the  basin  will  fill  with  water,  which  came 
out  of  the  kettle  in  the  condition  of  vapour.  Supposing 


Water  distilled  from  a  kettle. 

this  experiment  to  be  made  during  a  sharp  winter  frost, 
it  may  be  completed  by  setting  the  basin  out-of-doors 
where  the  water  will  gradually  grow  colder  and  colder 
until  it  is  frozen  into  ice  again,  as  at  first. 

Now,  in  this  experiment,  the  substance  of  the  water  is 
the  same  all  the  time,  but  we  see  it  pass  through  three 
different  states  or  conditions.  First,  it  was  in  a  solid 
state  of  ice,  then,  by  heating,  it  was  changed  into  a  liquid 
state  of  water,  and  heating  still  further  turned  it  into  a 
state  of  vapour  or  gas.  And  afterwards  some  of  it  was 
cooled  down  again  from  vapour  to  water,  and  from 
water  back  to  ice. 


SOLID-  LIQUID— GAS.  233 

When  we  come  to  think  of  it,  all  the  substances  that 
we  know  in  the  world  exist  in  one  or  other  of  these 
three  states — solid,  liquid,  or  gas.  We  could  name 
plenty  of  solid  substances,  such  as  iron,  and  wood,  and 
wax ;  there  are  liquids,  such  as  water,  and  oil,  and  quick- 
silver; and  there  are  gases,  such  as  the  coal-gas  we 
burn,  and  the  air  we  breathe.  The  water  was  changed 
from  one  condition  to  another  by  making  it  hotter  or 
colder,  and  water  is  a  very  convenient  example  to 
use,  because  we  are  all  so  familiar  with  it.  Every 
winter,  as  a  rule,  in  this  climate,  there  is  cold  enough 
to  freeze  it  into  ice  and  snow,  and  any  fire  gives  heat 
enough  to  turn  it  into  vapour.  But  changes  of  the 
same  kind,  though  generally  requiring  more  heat,  are 
constantly  made  in  other  substances.  Lead  and  tin  are 
melted,  or  fused,  as  we  say,  without  much  difficulty, 
and  also  no  one  who  has  seen  an  iron  foundry  can  ever 
forget  the  look  of  flowing  streams  of  molten  iron, 
quivering  with  heat.  Although  there  is  a  very  great 
difference  in  the  readiness  with  which  different  sub- 
stances will  change  their  condition,  yet  so  many  have 
actually  been  changed  by  experiment,  that  it  seems 
reasonable  to  believe  that  all  might  be  made  to  pass 
into  the  other  states  if  we  could  get  heat  or  cold  enough 
to  act  upon  them.  Even  air  has  been  made  liquid  and 
some  gases  solid  by  great  pressure  and  intense  cold. 

But  let  us  understand  exactly  what  we  mean  in  saying 
that  probably  all  solid  substances  might  be  melted  or 
vaporized,  and  all  liquids  turned  into  vapours,  if  they 
were  made  hot  enough.  There  are  plenty  of  solid  things 
all  round  us.  Here,  for  instance,  is  a  lump  of  coke;  could 


234  THE  FORCES  OF  NATURE. 

I  melt  that  by  heating  it?  Coke  consists  chiefly  of 
carbon,  which  is  one  of  the  most  difficult  substances  in  the 
world  to  fuse.  But  long  before  it  became  hot  enough  to 
melt,  something  else  would  happen.  A  very  moderate 
degree  of  heat  would  enable  the  carbon  to  combine 
with  the  oxygen  in  the  air,  and  it  would  all  burn  away, 
and  pass  into  the  state  of  gas  by  chemical  combination. 
It  would  be  necessary  to  prevent  any  oxygen  getting  to 
the  hot  carbon  if  we  were  really  to  tn7  and  melt  it ;  so 
that  we  should  not  succeed  by  merely  using  great  heat 
without  thinking  of  other  circumstances. 

Cohesion. — The  real  difference  between  the  three 
states  of  matter  is  a  difference  of,  or  absence  of, 
Cohesion.  The  cohesion  is  strongest  in  solid  bodies, 
and  the  most  perfect  solids  are  those  like  iron  or  granite, 
in  which  cohesion  offers  the  greatest  resistance  to  the 
other  forces  which  would  change  their  shape  or  size. 
Take  the  poker  from  the  fireplace  and  examine  it.  How 
strong  and  solid  it  is  !  It  will  neither  break,  nor  bend, 
nor  stretch,  nor  squeeze  with  any  force  of  our  hands. 
Many  solids,  however,  can  be  readily  broken  or  bent, 
and,  in  fact,  we  can  find  very  different  degrees  of  firmness 
among  them,  but  we  call  every  substance  solid  which  has 
cohesion  enough  to  keep  some  shape  of  its  own,  resisting 
the  force  of  gravitation  which  tries  to  draw  its  upper 
particles  down  among  the  lower.  In  this  sense  even  a 
lump  of  jelly  is  a  solid,  yielding  as  it  is  in  other  ways. 
Some  substances,  like  pitch  and  cobbler's  wax,  that  look 
solid,  and  are  even  brittle  to  a  blow,  gradually  yield  to  the 
force  of  gravitation,  and  flow  like  a  thick  liquid  if  time 
enough  be  given  :  such  bodies  are  called  viscous  solids. 


COHESION  OF  SUBSTANCES,  235 

In  liquids  the  cohesion  is  very  slight,  the  molecules 
moving  readily  over  each  other  in  any  direction,  so  that 
they  are  free  to  follow  the  guidance  of  gravitation. 
When  we  first  put  the  lump  of  ice  into  our  saucepan, 
you  remember  that  it  stood  up  with  an  irregular  shape 
of  its  own ;  but  when  it  melted  and  became  liquid, 
gravitation  drew  the  obedient  drops  trickling  downwards 
into  the  bottom  of  the  pan,  and  allowed  none  to  stand 
up  above  the  rest,  so  that,  when  all  was  melted,  the  top 
of  the  water  presented  a  level  surface. 

In  gases  or  vapours  (vapours  only  mean  gases  easily 
turned  into  liquids)  there  is  no  cohesion  at  all.  So  far 
are  their  molecules  from  holding  together,  that  they  are 
always  trying  to  spread  themselves  as  widely  apart  as 
possible,  and  thus  gases  readily  fly  off,  and  are  diffused 
into  the  air.  In  fact,  if  they  are  to  be  kept  separate  at 
all,  they  have  to  be  carefully  bottled  up. 

So  then,  if  the  cohesion  in  a  solid  substance  is  suf- 
ficiently lessened,  the  solidity  disappears.  If  a  little 
cohesion  is  left,  we  shall  have  a  liquid,  or,  if  the  cohesion 
is  quite  destroyed,  the  substance  will  fly  off  as  a  gas. 

Heat,  as  we  know,  is  the  great  enemy  of  cohesion,  and 
no  solid  or  liquid  can  hold  together  if  there  is  strong 
enough  heat  separating  its  particles ;  but  it  does  not  follow 
that  by  taking  away  the  heat  we  can  always  bring  back 
the  cohesion.  The  molecules  of  vapour  may  get  too 
far  apart  for  cohesion  to  act.  The  vapour  that  went  off 
from  the  boiling  saucepan  was  lost  in  the  air,  and  no 
one  could  bring  it  together  again  to  condense  it  back 
into  a  draught  of  water.  It  cools  down,  of  course,  in 
the  cool  air,  and,  though  some  may  be  condensed  again, 


236  THE  FORCES    OF  MATURE. 

in  the  form  of  rain  or  dew,  yet  much  may  remain  in  the 
state  of  diffused  vapour  even  when  the  air  is  cold  enough 
to  freeze  water. 

Evaporation. — Wherever  water,  or  even  ice,  has  an 
uncovered  surface  (either  in  air  or  a  vacuum),  some  of  it  is 
quietly  and  invisibly  passing  off  in  the  form  of  vapour, 
unless  the  air  is  so  full  of  water-vapour  already,  so 
damp,  as  we  say,  that  it  can  hold  no  more.  We  do  not 
notice  this  much  when  there  is  a  large  body  of  water, 
but  when  we  hang  up  wet  clothes  in  the  air  to  dry  we 
reckon  that  the  water  in  them  will  soon  evaporate,  or 
pass  off  in  vapour.  If  the  air  is  very  damp,  so  that  it 
will  not  take  much  more  water-vapour,  we  say  it  is  a 
bad  drying  day.  Hot  air  can  take  more  vapour  than 
cold  air,  so  that  in  hot  weather,  or  in  front  of  a  fire, 
things  will  dry  quicker ;  but,  then,  if  anything  cools  the 
air  it  can  no  longer  hold  so  much,  and  some  of  the 
vapour  condenses  into  water  again.  So,  after  a  hot, 
drying  day  in  summer,  when  the  sun  sets  and  the  air 
cools  down,  we  are  apt  to  have  a  heavy  dew,  which  is 
just  the  extra  vapour  in  the  air  deposited  in  the  form  of 
water  upon  the  cooled  grass.  But  next  morning,  when 
the  sun  has  been  up  some  time  and  the  air  is  warmed, 
it  will  drink  up  the  dew  again. 

Solution. — Here  is  a  solid  lump  of  sugar.  Put  it 
into  this  cup  of  water,  and  after  a  short  time  it  will 
have  disappeared.  The  cohesion  that  kept  it  solid  is 
lessened  by  the  affinity  that  water  has  for  the  sugar,  and 
it  has  passed  into  the  form  of  clear  liquid,  which  mixes 
with  the  water.  The  sugar  is  dissolved,  and  the  mixture 
is  called  a  solution  of  sugar. 


CR  YSTALLIZA  TION.  237 

Now,  if  we  go  on  putting  more  and  more  sugar  into 
the  cup,  it  will  continue  to  dissolve  for  some  time,  but 
at  last  the  water  will  have  taken  up  as  much  as  it  can 
hold ;  and  if  more  sugar  is  added  after  this  point  is 
reached  it  will  not  be  dissolved  at  all,  but  will  remain 
solid.  The  solution  is  then  said  to  be  saturated.  If  a 
saturated  solution  is  kept  in  an  open  vessel  where  air 
can  reach  it,  the  evaporation  which  constantly  goes  on 
at  the  surface  will  gradually  draw  away  the  water,  and 
the  dissolved  substance,  now  become  too  much  for  the 
diminishing  quantity  of  water,  will  slowly  reappear  in  a 
solid  form. 

Crystallization. — And  here,  for  the  first  time,  the 
force  of  cohesion,  or  molecular  attraction,  is  seen  doing 
active  work.  Hitherto  we  have  only  noticed  it  quietly 
resisting  the  active  work  of  other  forces ;  but  here,  as 
the  molecules  are  gradually  set  free  from  the  water,  each 
begins  to  be  drawn  into  its  place  and  built  into  the  solid 
mass.  And  how  wonderful  and  beautiful  is  the  building  ! 
When  the  attracting  force  is  not  interfered  with  in  any 
way, — that  is,  when  the  solidifying  is  slow  enough,  and 
there  is  plenty  of  time,  and  plenty  of  room  for  the  work, 
and  the  solution  is  quite  still  and  unshaken, — the  new 
solid  will  frequently  appear  in  the  form  of  regular 
crystals,  often  clear  and  transparent,  small  at  first,  but 
gradually  increasing  in  size  as  fresh  layers  of  molecules 
are  deposited ;  and  every  crystal  has  its  own  fixed  form, 
always  the  same  for  the  same  substance. 

Take  a  lump  of  alum,  and  put  it  into  a  tumbler 
with  just  cold  water  enough  to  cover  it.  In  a  few  days 
we  shall  find  its  surface  eaten  out  into  a  variety  of  forms 


238 


THE  FORCES  OF  NATURE. 


more  or  less  regular.  If  we  now  put  a  drop  of  the 
water  on  to  a  slip  of  glass,  and  set  it  on  the  chimney- 
piece  in  very  gentle  warmth,  we  shall  find,  as  it  slowly 
evaporates,  that  the  alum  dissolved  in  it  reappears  in 
the  form  of  tiny,  eight-sided  crystals,  which  may  be 
easily  examined  with  a  magnify- 
ing glass.  Some  of  them  .will 
very  likely  look  as  if  their 
corners  or  their  edges  had  been 
cut  away,  but  all  preserve  the 
same  general  form ;  and  we  re- 
cognize the  same  forms  also 
carved  out  by  the  water  in  the 
Here  is  a  picture  of  a  big  group 
of  alum  crystals,  as  they  are  formed  in  the  slow  cooling 
of  a  strong  solution. 

Dissolve  a  teaspoonful  of  common  salt,  of  Epsom  salt, 
and  of  nitre,  each  in  a  different  wine-glass  of  water,  and 
let  them  stand  till  next  day.  Then  put  a  drop  of  each 
as  before,  on  slips  of  glass,  where  they  may  evaporate 
slowly.  As  they  dry  up  the  salt  will  appear  in  tiny 


Epsom 


Group  of  alum  crystals. 

larger  mass  of  alum. 


A  crystal  of  alum.        Common  Salt. 


cubes,  the  Epsom  salt  in  four-sided  prisms,  and  the  nitre 
in  six-sided  prisms.  Here  we  can  compare  crystals  of 
different  forms,  each  form,  however,  belonging  invariably 
to  its  own  proper  substance. 

Look  at  a  lump  of   loaf  sugar  and  a  piece  of  sugar 


MAKING  CRYSTALS.  239 

candy.  They  are  both  sugar  ;  but  why  do  they  look 
so  different  ?  The  candy  has  crystals  sharply  and  regu- 
larly formed,  while  the  lump  seems  to  be  a  mere  mass 
cf  crystalline  grains  crowded  together,  in  which  we  can- 
not make  out  any  regular  forms.  This  difference  depends 
on  the  rapidity  or  slowness  of  the  evaporation.  If  the 
solution  is  rapidly  and  hurriedly  evaporated,  the  crystals 
produced  are  confused  and  minute  j  to  get  them  perfect 
in  form,  the  solution  should  be  kept  very  still  and  com- 
paratively cool,  that  it  may  evaporate  slowly. 

The  following  pretty  experiment  is  sure  to  please  those 
who  carry  it  out  carefully  and  patiently.  Take  some 
fine  wire  with  a  little  thread  wound  round  it,  and  twist 
it  into  the  outlined  form  of  a  small  basket.  Then  make 
a  saturated  solution  of  alum  in  water  in  the  following 
way.  Take  rather  more  boiling  water  than  will  be 
needed  to  cover  the  basket,  and  dissolve  powdered  alum 
in  it  until  it  will  dissolve  no  more.  Strain  the  solution 
through  a  piece  of  muslin,  when  it  should  be  poured  into 
a  wide-mouthed  jar.  Tie  a  loop  of  thread  round  the 
basket  handle,  pass  a  piece  of  stick  through  the  thread 
and  gently  lower  the  basket  into  the  solution.  The 
basket  must  be  completely  covered  by  the  liquid,  but 
must  not  touch  the  sides  or  bottom  of  the  jar ;  it  will 
be  kept  in  its  place  by  resting  the  stick  across  the  top 
of  the  jar.  Then  put  the  whole  away  for  four  or  five 
days  into  some  place  where  it  will  not  be  touched  or 
shaken ;  if  possible  it  should  be  locked  into  a  closet 
where  there  will  be  no  sweeping  or  dusting.  The  crystals 
of  alum  will  be  deposited  in  clusters  on  the  wires,  turning 
them  into  a  crystal  basket,  but  the  whole  befrig  evenly 


240  THE  FORCES  OF  NATURE. 

covered  depends  chiefly  on  the  jar  remaining  entirely 
undisturbed  during  the  process.  If  a  little  colouring 
matter  is  mixed  with  the  solution,  we  can  obtain  coloured 
crystals. 


(     241     ) 


CHAPTER   XVI. 

HEAT. 

Expansion. — We  have  already  had  occasion  to  talk  a 
little  about  Heat  while  studying  Cohesion  and  Gravita- 
tion, and  have  seen  that  it  is  often  at  work  overcoming 
Cohesion,  and  making  the  density  of  substances  less  and 
their  size  larger.  Here  is  an  experiment  to  show  us  a 
solid  substance  growing  larger,  or  expanding,  with  heat. 

Take  a  common  steel  knitting-needle,  K,  K  (p.  242),  and 
with  a  vice  or  clamp,  c,  fasten  it  in  a  horizontal  position 
and,  securely  at  one  end,  to  a  block  of  wood,  b.  Get 
another  block  of  wood  or  a  book,  //,  and  on  it  place  a  bit 
of  window  glass,  g,  and  on  the  glass  a  sewing-needle,  ;/, 
the  end  of  this  needle  is  only  seen  in  the  picture.  Fix  a 
straw,  or  any  light  index,  /,  on  to  the  point  of  the  sewing 
needle,  and  hang  a  letter-weight,  W,  to  the  free  end 
of  the  knitting-needle  to  keep  it  pressed  down.  If  the 
knitting-needle  is  now  heated  by  putting  a  spirit-lamp, 
L,  under  it,  it  will  expand  and  grow  longer;  but  the 
change  of  length  would  be  too  small  for  us  to  see,  were 
it  not  that  the  end  of  the  needle  in  advancing  rolls 
the  sewing-needle  round,  and  so  makes  the  long  index 
swing  round  quite  perceptibly.  It  is  a  good  plan  to  set 
up  behind  the  block  a  screen  with  a  straight  upright  line 

R 


242 


THE  FORCES  OF  NATURE. 


drawn  on  it  parallel  with  the  index,  t,  so  that  we  can 
measure  how  much  the  index  moves  away  from  the 
upright. 

In  this  case  we  have  a  very  small  steel  rod  lengthened 
by  heat,  and  the  large  iron  rails  of  the  railways  lengthen 
in  just  the  same  way  in  hot  weather.  If  their  ends  were 
fixed  close  to  each  other  while  they  were  cool,  then  their 
expansion,  when  it  came,  would  make  them  thrust  each 


Experiment  Illustrating  Expansion  by  Heat. 


other  upwards  or  sideways,  and  so  break  the  straight 
line  of  the  rails.  But  next  time  you  are  near  a  railway, 
go  and  look  attentively  at  the  rails  where  they  join,  and 
you  will  find  that  there  is  always  a  space  left  between 
them  to  allow  for  their  lengthening. 

To  see  a  liquid  expand  with  heat,  let  us  examine  an 
ordinary  THERMOMETER.*  You  see  that  at  its  lower  end 

*  Thermometer — "measure  of  heat,"  though,  as  we  shall  see 
directly,  the  thermometer  is  really  a  measure  of  temperature,  not  of 
the  quantity  of  heat  in  a  substance. 


THE    THERMOMETER.  243 

is  a  hollow  glass  ball  or  bulb,  with  a  narrow  glass  tube 
rising  out  of  it,  and  that  the  bulb  and  part  of  the  tube 
contain  mercury.  As  in  the  barometer  so  here  the 
closed  end  of  the  tube  above  the  mercury  has  been 
emptied  of  air.  The  bulb  and  tube  are  usually  set  in 
a  frame,  on  the  back  of  which  is  a  scale  of  figures.  Hold 
the  bulb  in  your  warm  hand,  and  as  the  warmth  reaches 
the  mercury  it  expands  and  rises  higher  in  the  tube ; 
put  it  in  front  of  the  fire  and  it  will  rise  still  higher ;  you 
can  note  the  height  on  the  scale  at  the  back.  Plunge 
it  into  cold  water ;  the  water  withdraws  heat  from  it,  and 
the  mercury  contracts  and  falls. 

In  order  to  make  a  scale  for  measuring  the  amount 
of  rise  and  fall,  the  thermometer  is  plunged  first  into 
melting  ice  for  a  few  minutes ;  and  when  the  mercury 
has  left  off  falling,  and  is  quite  steady,  its  height  is  clearly 
marked  on  the  frame.  Next,  it  must  go  into  boiling 
water — not  merely  very  hot  water,  but  water  actually 
boiling  and  bubbling.  Up  rushes  the  mercury  at  first, 
but  presently  it  comes  to  a  stand  and  will  rise  no  higher. 
When  it  is  steady,  this  height  also  is  marked.  These  two 
fixed  points  are  called  the  freezing  point  and  the  boiling 
point.* 

But  now  comes  the  practical  difficulty  in  our  use  of 

*  As  the  boiling  point  varies  slightly  with  the  nature  of  the  vessel 
in  which  the  water  is  boiled,  and  considerably  with  the  elevation 
above  the  sea  level,  the  true  boiling  point  is  that  given  by  the 
steam  from  water  boiling  in  an  open  vessel  at  the  level  of  the  sea, 
when  the  barometer  is  standing  at  30  inches  high.  For  as  the 
pressure  of  the  atmosphere  decreases  the  boiling  point  falls.  On 
the  top  of  Mont  Blanc,  for  instance,  which  is  nearly  16,000  feet 
above  the  sea,  water  boils  at  185°  F.,  whereas  at  the  sea  level  it 
boils  at  212°  F. 


244  THE  FORCES  OF  NATURE. 

thermometers,  which  is  that  instead  of  all  agreeing  to 
use  one  scale  of  figures,  people  use  two  or  three  different 
scales.  One  plan,  which  seems  the  most  sensible,  is  to 
call  the  freezing  point  o,  and  the  boiling  point  100,  and 
to  divide  the  space  between  them  into  100  equal  parts 
or  degrees.  A  thermometer  marked  on  this  plan  is  called 
a  Centigrade*  thermometer,  and  is  generally  used  in 
scientific  work.  But  unfortunately  on  the  thermometers 
in  common  use  in  this  country  the  freezing  point  is 
marked  32,  and  the  boiling  point  212,  the  space  between 
them  being  divided  into  180  degrees.  This  is  called 
the  Fahrenheit  thermometer  from  the  name  of  the 
inventor,  and  you  can  see  that  nine  degrees  of  the 
Fahrenheit  thermometer  are  equal  to  five  degrees  of 
the  Centigrade.  It  is  necessary  to  be  acquainted  with 
both  of  these  scales,  and  we  generally  find  that  measure- 
ments of  heat  in  books  are  marked  C.  or  F.,  to  show 
which  is  intended  to  be  used.  Thus  100°  C.  =  212°  F. 
must  be  understood  to  mean,  one  hundred  degrees  Centi- 
grade represents  the  same  temperature  as  two  hundred 
and  twelve  degrees  Fahrenheit.  If  the  warmth  of  your 
sitting-room  is  60°  F.  it  will  mark  not  quite  16°  on  a 
Centigrade  thermometer.  Notice  that  the  word  degree 
is  indicated  by  the  little  sign  °  placed  after  the  figure, 
thus  1 6°  C.,  means  16  degrees  Centigrade. 

Temperature. — Now  that  we  have  our  thermometer, 
let  us  see  exactly  what  it  is  that  is  measured  by  it. 
It  is  not  the  amount  of  heat  that  any  substance 
has  received,  but  what  we  call  its  temperature,  or  the 
degree  of  hotness  which  it  has  reached.  We  will  try  to 
*  Centigrade,  hundred  steps. 


WHAT  THE   THERMOMETER  MEASURES.     245 

understand  this  quite  clearly,  as  mistakes  are  often  made 
about  it. 

If  we  put  side  by  side  on  a  table  a  small  medicine 
bottle,  a  tumbler,  and  a  glass  dish  or  pan,  and  pour  into 
each  of  them  exactly  the  same  quantity  of  water — say, 
a  small  teacupful — it  will  fill  up  the  bottle  to  the  top, 
the  tumbler  will  be  half  full,  while  the  dish  will  barely 
have  the  bottom  covered  (see  picture).  The  quantity  of 
water  is  the  same  in  each,  but  the  different  shapes  of  the 
vessels,  and  especially  the  different  size  of  the  bottom, 


Experiment  illustrating  analogy  of  water  level  and  temperature. 

makes  all  the  difference  in  the  level  to  which  the  water 
rises. 

If  we  next  place  in  front  of  the  vessels  a  screen  with 
a  narrow  slit  in  it,  which  will  only  allow  a  narrow  upright 
section  to  be  seen,  and  then  invite  some  one  who  is  not 
in  the  secret  to  look  at  each  vessel  through  the  slit,  he 
will  certainly  think  that  the  bottle  contains  the  most 
water;  and  if  we  assure  him  that  the  same  quantity  was 
poured  into  all,  he  may  say,  "  Well,  I  do  not  know  where 
the  rest  of  the  water  is  gone,  but  it  certainly  is  not  filling 
them  up  to  the  same  level." 

Now  this  is  exactly  as  much  as  the  thermometer  can 
tell  us  about  the  heat  of  substances.  It  cannot  tell  how 


246  THE  FORCES  OF  NATURE. 

much  heat  they  may  have  received,  or  what  else  it  may 
be  doing,  but  can  only  show  the  temperature^  or  the  level 
at  which  the  intensity  of  the  heat  in  them  stands. 

Again,  if  we  were  to  stand  the  bottle  of  water  in  the 
dish,  and  then  knock  a  hole  in  the  side  of  the  bottle 
(near  the  bottom),  the  water  would  flow  out  until  all  in 
the  bottle  and  dish  stood  at  the  same  level.  Just  so, 
when  we  bring  into  contact  two  bodies  of  different  tem- 
peratures, the  heat  will  pass  from  the  higher  temperature 
to  the  lower  until  both  stand  at  the  same  level. 

Let  us  look  at  some  cases  where  the  same  amount  of 
heat  applied  raises  temperature  to  different  levels.  Put 
on  to  the  same  fire,  and  as  nearly  as  possible  in  equally 
good  positions  over  the  hot  coals,  two  saucepans  of  the 
same  size,  one  quite  full  of  water  fresh  from  the  pump, 
and  the  other  with  merely  an  inch  of  the  same  fresh 
water  in  the  bottom,  and  place  a  thermometer  in  each. 
See  how  quickly  the  temperature  rises  in  the  inch  of 
water ;  it  will  reach  the  boiling  point  before  the  other  is 
warmed  through,  and  when  it  does  so  we  will  take  both 
of  them  off  the  fire.  They  are  now  exactly  in  the  same 
position  with  regard  to  heat  as  the  bottle  and  dish  with 
regard  to  the  water.  Both  have  received  the  same 
amount  of  heat,  but  one  is  raised  to  a  high  level  of 
temperature,  while  the  other,  owing  to  the  larger  quantity 
of  water  over  which  the  heat  had  to  be  spread,  stands 
at  a  much  lower  level. 

Specific  Heat. — In  this  case  the  difference  of  tem- 
perature depends  only  on  the  different  quantity  of  liquid 
to  be  heated ;  but  we  will  now  vary  the  experiment  thus. 
Take  two  small  vessels  of  equal  size  and  thickness  (the 


SPECIFIC  HEAT.  Itf 

small  glass  fish-bowls  sometimes  used  for  flowers  are 
very  convenient),  and  put  into  one  a  certain  weight 
of  water,  and  into  the  other  the  same  weight  of  turpentine. 
Place  a  thermometer  in  each,  and  make  sure  that  they 
are  hoth  at  exactly  the  same  temperature.  If  they  are 
not  so  at  first,  let  them  stand  near  together  in  the  same 
room  for  some  time,  and  they  will  both  have  the  tem- 
perature of  the  air  in  the  room,  for  whichever  is  hotter, 
air,  water,  or  turpentine,  will  give  up  some  of  its  heat  to 
the  others  until  all  stand  at  the  same  level.  When  they 
are  equal,  put  them  both  together,  with  the  thermometers 
still  in  them,  into  a  pan  of  warm  water.  You  will  find 
that  when  the  thermometer  in  the  water-bowl  has  risen 
one  degree,  the  thermometer  in  the  turpentine  will  have 
risen  about  two  degrees  or  a  little  more. 

Here  the  quantities  by  weight  of  water  and  turpentine 
are  the  same,  and  the  quantity  of  heat  given  to  each  is 
the  same,  yet  it  takes  more  than  double  the  amount  of 
heat  to  raise  the  temperature  of  water  one  degree  than 
it  does  to  raise  the  temperature  of  turpentine  one  degree. 

If  we  tried  other  substances,  we  should  find  that  they 
vary  a  good  deal  from  one  another  in  the  readiness  with 
which  their  temperatures  can  be  raised;  but  they  may 
all  be  measured  against  water,  and  the  heat  that  each 
requires  to  warm  it,  say  one  degree  compared  with  the 
heat  an  equal  weight  of  water  requires,  is  called  the 
specific  heat  of  the  substance — just  as  the  weight  of 
each,  compared  with  the  weight  of  an  equal  bulk  of  water, 
is  called  the  specific  gravity.  No  other  solid  or  liquid 
substance  requires  so  much  heat  to  raise  its  temperature 
as  water  does,  so  if  we  call  the  specific  heat  of  water  i, 


248  THE  FORCES   OF  NATURE. 

we  shall  find  the  specific  heats  of  all  these  other  sub- 
stances to  be  less  than  i,  so  that  they  must  be  expressed 
by  fractions.  The  specific  heat  even  of  ice  is  less  than 
half  that  of  water,  or  0*5  ;  of  turpentine  is  0*43  ;  of  iron 
o'u  ;  of  mercury  only  0-033,  or  one-thirtieth  of  an  equal 
weight  of  water,  so  that  mercury  is  an  excellent  indicator 
for  the  thermometer,  as  its  temperature  rises  so  rapidly 
with  small  additions  of  heat.  We  must  remember,  how- 
ever, that  mercury  is  13^  times  heavier  than  water.  It 
is  on  account  of  its  regular  expansion  through  a  wide 
range  of  temperature — owing  to  its  boiling  at  a  very 
high  temperature,  and  freezing  at  a  low  one — that  mercury 
is  usually  chosen  for  thermometers. 

Fusion. — LATENT  HEAT.— We  have  already  tried  ex- 
periments in  turning  ice  into  water,  and  water  into  vapour 
(see  p.  231);  but,  now  that  we  understand  the  meaning 
and  use  of  the  thermometer,  we  will  take  them  over  again, 
making  more  exact  observations.  Before  bringing  in 
the  lump  of  ice  let  us  make  a  hole  in  it  to  hold  the 
bottom  of  our  thermometer  and  note  the  temperature  : 
usually  it  will  be  32°  F.,  the  freezing-point  of  water, 
unless  the  air  is  very  cold  and  below  the  freezing-point. 
Now  put  the  ice  in  a  pan  near  the  fire  and  watch  the 
thermometer,  it  remains  stationary.  The  heat  continually 
added  to  the  ice  is  no  longer  raising  the  level  of  its 
temperature ;  it  is  doing  other  work,  breaking  down  the 
crystalline  order  and  overcoming  the  cohesion — in  other 
words,  it  is  melting  the  ice ;  and  until  every  particle  of 
the  ice  is  changed  into  water,  we  shall  see  no  alteration 
in  the  thermometer."'  There  are,  however,  other  ways  of 

*  The  ice  and  water  must  be  kept  well  stirred  through  this  time. 


LATENT  HEAT.  249 

ascertaining  the  amount  of  heat  which  is  taken  in  all 
through  the  time  of  melting;  and  it  is  known  that  the 
ice  takes  as  much  heat  to  melt  it  as  would  serve  to  raise 
the  temperature  of  an  equal  weight  of  water  nearly  80°  C. 
or  144°  F.,  that  is,  from  32°  to  176°  F.  When  all  this 
heat  has  been  expended  in  overcoming  the  internal 
forces,  and  the  whole  ice  is  converted  into  water,  the 
thermometer  in  it  still  stands  at  32°  F.  But  the  instant 
this  work  is  done,  any  further  heat  added  now  affects 
the  level  of  temperature,  and  the  thermometer  again 
begins  to  rise. 

We  will  now  put  the  saucepan  of  water  on  the  fire  and 
the  rise  steadily  continues  until  the  thermometer  indicates 
212°  F.  (100°  C.)  or  boiling-point.  Here,  again,  it  stands 
still,  and  never  rises  above  this  point  while  the  whole  of 
the  water  is  being  converted  into  vapour.  The  additional 
heat  now  taken  in  for  this  purpose  is  enormous.  To  turn 
one  pound  of  boiling  water  entirely  into  steam  at  the 
same  temperature  requires  as  much  heat  as  would  raise 
965  pounds,  or  8-^  hundred-weights,  of  water  i°  F.  This 
amount  of  heat  would  raise  nearly  5-^-  pounds  of  water 
from  the  freezing-point  to  the  boiling-point.  But  none 
of  the  heat  used  in  changing  the  pound  of  water  into 
steam  becomes  apparent  in  the  temperature ;  it  is  at 
work  destroying  cohesion,  and  setting  the  molecules 
absolutely  free  from  each  other's  attraction.  You  know 
that  evaporation  from  the  surface  was  going  on  before, 
and  you  have  seen  steam  rising  from  the  water  all  the 
time  it  was  heating ;  but  the  difference  when  the  boiling 
point  is  reached  is  that  the  temperature  rises  no  more 
until  the  whole  liquid  is  converted  into  vapour. 


250  THE  FORCES   OF  NATURE. 

Heat  which  thus  passes  altogether  out  of  sight,  un- 
recognized by  the  thermometer,  is  given  the  name  of 
latent,  or  hidden,  heat. 

But  when  the  process  is  reversed — when  vapour  is 
cooled  and  condensed  into  water,  it  sets  free  again  all 
the  heat,  the  latent  heat  of  evaporation,  that  was  taken 
up  in  vaporizing  it.  and  when  water  freezes  into  ice  it 
sets  free  the  latent  heat  of  fusion  which  was  before 
absorbed  in  melting  it,  and  the  heat  thus  set  free  becomes 
again  what  is  called  sensible  heat,  that  is,  heat  that  can 
be  felt. 

This  makes  the  freezing  take  place  very  gradually. 
When  water  is  chilled  down  to  a  temperature  of  32°  F. 
it  does  not  all  suddenly  become  solid ;  but  as  it  begins 
to  solidify  heat  is  set  free  in  the  proportion  of  144°  F. 
for  every  pound  of  the  water,  and  the  whole  of  this  must 
be  taken  away  by  the  chilling  process  before  the  work  of 
freezing  is  finished.  On  the  other  hand,  when  ice  is 
melting,  it  does  not  all  suddenly  become  liquid  when  the 
thermometer  rises  above  freezing-point ;  but  before  the 
melting  is  finished  it  must  find  for  every  pound  of 
the  ice  as  much  heat -as  would  raise  the  temperature  of 
a  pound  of  water  144°  F.  And  fortunate  it  is  for  us  that 
the  work  has  to  proceed  so  slowly,  else  every  slight  frost 
would  deprive  us  of  all  our  water,  and  every  thaw  after 
frost  and  snow  would  mean  a  devastating  flood,  with  no 
time  for  the  water  to  run  off  as  it  melted. 

Density  of  Ice  and  Water.— Solid  bodies,  as  they 
liquefy  under  heat  and  have  their  cohesion  made  less, 
generally  become  less  dense  at  the  same  time,  the 
molecules  moving  farther  and  farther  apart  and  being 


ICE  AND    WATER.  251 

spread  over  more  space,  so  that  the  liquid  form  of  a 
substance  is  almost  always  lighter  than  an  equal  bulk  of 
the  solid  form.  But  two  or  three  substances,  of  which 
water  is  the  most  easily  observed,  are  densest  when  they 
are  at  a  temperature  rather  above  their  freezing-point,  so 
that  ice  is  lighter  than  an  equal  bulk  of  ice-cold  water. 
The  largest  number  of  men  may  be  squeezed  into  the 
smallest  space  when  they  are  crowded  together  anyhow  ; 
but  if  they  are  ranged  in  regular  order  like  companies  of 
soldiers  they  will  take  more  space,  or  if  the  crowd  move 
apart  a  little,  it  will  be  less  dense  and  also  take  more 
space.  Let  us  think  of  our  water  molecules  as  the 
men.  They  are  densest  and  most  closely  crowded 
together  at  a  temperature  of  about  39^°  F. ;  but  as  the 
temperature  falls  to  freezing-point  they  are  ranged  into 
their  crystalline  order,  and  so  expand  and  take  more 
room,  or  as  the  temperature  rises  they  move  apart  and 
also  take  more  room,  and  so  the  density  becomes  less 
either  way. 

It  is  a  happy  thing  for  the  world  that  ice  is  lighter 
than  water.  Only  think  what  would  happen  if  it  were 
not  so  !  As  soon  as  the  surface  of  water  became  chilled 
by  the  cold  air  and  froze,  the  ice,  if  it  were  heavier, 
would  sink  to  the  bottom  and  leave  the  next  layer  of 
water  on  the  top  to  be  frozen  and  sink  in  the  same  way, 
till  the  whole  mass  of  water  was  changed  into  solid  ice 
in  which  no  fish  could  live.  As  it  is,  however,  the  layer 
of  ice  remains  floating  on  the  top  and  makes  a  shield  for 
the  water  underneath  from  the  cold  air. 

Force  of  Expansion. — But  ice  is  lighter  because 
larger  than  the  unfrozen  water,  and  when  it  wants  more 


252  THE  FORCES   OF  NATURE. 

room  it  will  have  more  room.  If  water  in  our  water-pipes 
is  chilled  enough  to  expand  into  ice  and  wants  more 
room  for  the  crystalline  arrangement,  it  will  make  nothing 
of  bursting  open  the  iron  pipe  to  obtain  it ;  and  yet  the 
difference  of  size  between  ice  and  water  is  not  so  very  great. 
What,  then,  must  be  the  expansive  force  of  water  changing 
into  steam,  for  their  difference  of  size  is  enormous  ! 
When  the  molecules  are  quite  set  free  from  cohesion, 
the  water  expands  into  vapour  1700  times  its  own 
volume;  a  pint  of  water  will  make  1700  pints  of  water 
vapour.  Have  not  you  noticed  how,  when  water  is  boil- 
ing in  a  covered  saucepan,  the  steam  keeps  lifting  the  lid 
and  letting  itself  out  in  clouds  far  larger  than  the  water 
it  came  from  ?  Every  kettle-lid  has  a  hole  in  it  to  let 
out  steam ;  but  if  the  steam  is  formed  rapidly  it  needs 
more  room  and  keeps  the  kettle-lid  dancing  in  the  same 
manner.  But  what  would  happen  if  the  lid  would  not 
open  and  the  hole  and  spout  were  stopped  ?  There  would 
soon  be  an  end  of  the  kettle;  and  the  expansion  of 
steam,  not  content  with  merely  cracking  it  open,  as  the 
ice  did  to  the  water-pipe,  would  explode  it  in  all  direc- 
tions with  such  force  as  to  wreck  everything  round  it. 

We  are  not,  however,  to  suppose  that  it  is  impossible 
to  prevent  these  expansions;  since  both  ice  and  steam 
are  hindered  from  forming  by  sufficiently  strong  pressure  ; 
but  the  strength  of  the  expansive  force  can  be  estimated 
by  the  great  strength  of  materials  that  is  required  to 
resist  it,  and  boiler  explosions  take  place  often  enough  to 
remind  us  what  a  giant  we  have  to  deal  with  in  imprisoned 
steam. 

Convection. — How  does  heat  spread  through  water? 


CONVECTION.  253 

We  put  cold  and  hot  water  together  to  fill  a  warm  bath, 
and  bring  them  to  the  same  warmth  throughout  by 
rapidly  stirring  them  together  and  mixing  them  with  the 
hand.  Would  they  have  mixed  themselves  if  left  alone  ? 
Yes,  if  the  hot  water  were  at  the  bottom  and  the  cold 
at  the  top,  for  the  hot  water  is  lighter  and  would  rise  and 
float  while  the  colder  water  sank,  and  as  the  currents 
pass  and  touch  one  another,  heat  would  be  given  up 
from  the  hotter  water  to  the  cooler  until  both  were 
equal.  But  no,  if  the  hot  water  were  on  the  top  to 
begin  with ;  for  then  there  would  be  nothing  to  set  any 
currents  moving  in  the  water. 

Put  a  saucepan  of  cold  water  on  the  fire  with  a  little 
soaked  sawdust  in  it  to  show  the  currents,  and  as  the 
bottom  water  gets  warm  first,  you  will  see  that  it  is 
always  rising  up,  while  the  colder  water  above  is  ever 
sinking  down  to  take  its  place  and  be  warmed  in  its 
turn. 

If  we  have  a  cup  of  tea  too  hot  to  drink,  and  simply 
let  it  stand  to  get  cool  it  will  cool  from  the  top,  the 
cooler  tea  will  sink  while  the  hotter  rises,  a  current  will 
be  set  up  mixing  it  thoroughly,  and  the  tea  will  be 
uniformly  cooled  through.  But  if  we  are  in  a  hurry, 
and  stand  the  cup  of  tea  in  a  deep  saucer  of  cold  water 
to  chill  it,  we  have  carefully  to  keep  stirring  it  with  a 
spoon,  for  now  the  bottom  tea  being  cooled  first,  it  will 
lie  still  at  the  bottom,  and  no  current  will  be  set  up 
unless  it  is  stirred. 

This  mixing  of  hotter  and  colder  parts  by  the  move- 
ment of  currents  is  called  convection,  and  is  the  usual 
way  in  which  heat  spreads  through  liquids  and  gases. 


254  THE  FORCES   OF  NATURE. 

Every  cook  knows  that  she  must  not  leave  a  pan  or 
kettle  on  the  fire  without  some  water  in  it.  As  long  as 
it  contains  water  the  heat  which  the  fire  pours  into  it 
all  passes  into  the  water,  first  raising  its  temperature,  by 
means  of  convection,  to  boiling-point,  and  then  turning 
it  into  vapour ;  but  as  soon  as  the  water  is  all  vaporized 
and  gone,  the  heat  will  set  to  work  upon  the  kettle 
itself,  and  soon  make  a  hole  in  it.  Convection  currents 
carry  off  the  heat  so  quickly  that  water  may  even  be 
boiled  in  paper.  This  pretty  experiment  is  easily  carried 
out.  Make  a  square  sheet  of  writing-paper  into  a  deep 
tray  by  turning  up  the  edges  all  round  and  folding  over 
the  corners,  put  a  little  water  in  it,  set  it  over  a  spirit- 
lamp  with  a  small  wick  so  that  the  flame  touches  only 
the  centre  of  the  paper,  and  the  heat  will  boil  the  water 
without  burning  the  paper.  A  stand  to  carry  the  tray 
may  be  readily  contrived  by  supporting  a  wire  ring  on 
three  legs  of  twisted  wire. 

Conduction. — Go  into  a  room  without  a  fire,  and  lay 
your  hand  by  turns  on  the  carpet,  the  table,  the  stone 
chimneypiece,  and  the  iron  fender.  Which  feels  the 
coldest  ?  The  carpet  does  not  feel  cold  at  all,  the  wood 
hardly  at  all,  while  the  stone  is  decidedly  cold,  and  the 
iron  colder  still.  But  they  have  all  been  standing  there 
long  enough  to  have  the  same  temperature  as  the  air  of 
the  room.  Let  us  fetch  a  thermometer  and  test  their 
temperature.  It  stands  at  the  same  level  in  all.  Is 
there,  then,  anything  in  the  room  of  a  different  tem- 
perature ?  Yes,  you  are  hotter,  and  your  hand  is  hotter 
than  the  rest  of  the  things.  When  you  lay  it  on  the 
iron  the  nearest  particles  are  warmed  by  your  warm 


COND  UCTION.  255 

hand.  How  does  the  heat  spread  through  the  iron  ?  It 
cannot  be  by  moving  currents,  for  in  solid  bodies  each 
particle  keeps  its  own  place,  and  they  cannot  be  driven 
about  among  each  other  like  streams  of  water.  In  this 
case  the  particles  that  are  warmed  first  pass  on  some  of 
their  heat  to  the  next,  and  these  again  to  the  particles 
beyond  them,  thus  gradually  spreading  the  heat  through 
the  whole  mass  by  what  is  called  the  process  of 
conduction. 

Iron  particles  pass  on  the  heat  rapidly,  taking  up 
more  and  more,  and  trying  quickly  to  bring  your  hand 
and  the  iron  to  the  same  low  level  of  temperature.  The 
stone  tries  to  do  the  same,  but  is  not  quite  so  active  in 
the  work,  so  that  it  does  not  chill  you  down  so  fast. 
The  wood  is  decidedly  slower  about  it,  and  when  the 
particles  nearest  the  hand  have  reached  its  temperature 
they  are  content  to  stay  so,  without  hurrying  to  pass  on 
the  heat.  And  the  particles  in  the  woollen  carpet  hardly 
move  in  the  matter  at  all. 

So  we  see  that  just  as  substances  differ  in  the  amount 
of  heat  required  to  raise  their  temperature,  so  they  also 
differ  very  much  in  the  rate  at  which  they  pass  on  their 
heat.  Those  which  pass  it  on  rapidly  are  called  good 
conductors.  But  some  are  so  slow  about  passing  on 
heat,  that  one  part  of  the  substance  may  be  actually 
burned  before  the  rest  of  it  is  heated  at  all.  These 
are  bad  conductors.  When  we  want  to  light  a  candle, 
we  either  strike  a  match,  or  twist  up  a  paper  spill 
and  light  it  at  the  fire ;  but,  in  either  case,  not  only  is 
one  end  of  the  match  cool  enough  to  hold  in  the  hand 
while  the  other  is  burning,  but  we  can  still  hold  it  until 


256  THE  FORCES  OF  NATURE. 

the  flame  almost  reaches  the  fingers.  It  is  plain  that 
wood  and  paper  are  bad  conductors. 

Wool  is  one  of  the  worst  of  conductors,  and  therefore 
it  makes  the  warmest  clothing;  for  while  it  does  not 
itself  conduct  away  the  heat  of  our  warm  bodies,  it 
makes  a  thick  screen  preventing  the  cold  air  from 
approaching  to  rob  us  of  heat.  But,  for  the  same  reason, 
it  is  the  best  protection  for  anything  cold,  and  we  wrap 
ice  in  flannel  to  prevent  its  melting,  for  the  flannel 
does  not  readily  allow  anything  else  warm  to  come  near, 
from  which  the  ice  could  borrow  heat  to  melt  with. 

The  best  conductors  are  the  metals,  but  they  are  not 
all  equally  good.  You  know  that  iron  is  a  pretty  good 
conductor,  yet  it  is  possible  to  hold  one  end  of  a 
tolerably  long  poker  in  the  hand  while  the  other  end  is 
red  hot.  If,  however,  the  poker  were  of  silver  no  one 
could  touch  it.  Silver  is  so  good  a  conductor  of  heat 
that  it  excels  all  other  conductors  in  this  respect. 
A  silver  spoon  left  for  a  minute  in  a  hot  cup  of  tea 
burns  one's  fingers,  where  a  plated  spoon,  that  is,  one 
of  commoner  metal  merely  coated  with  silver,  would 
remain  comparatively  cool.  A  silver  teapot  quickly  takes 
the  temperature  of  the  hot  tea  which  it  contains,  and  if 
the  silver  were  continuous,  the  handle  would  be  too  hot 
to  hold;  so  that  silver  teapots  are  always  made  with  a 
little  strip  of  ivory  on  each  side  of  the  handle  to  cut  off 
the  conduction  of  heat. 

Radiation.— There  is  another  very  important  way  in 
which  heat  passes  from  one  place  to  another.  When 
the  sun  shines  and  makes  us  feel  hot,  the  heat  travels 
all  the  long  way  from  the  sun  to  the  earth,  but  it  does 


LUMINIFEROUS  ETHER.  2$? 

not  come  by  convection  nor  yet  by  conduction ;  there 
are  no  heated  currents  set  up  which  flow  in  our  direc- 
tion, nor  is  it  handed  on  from  particle  to  particle 
through  the  air.  Indeed,  the  air  may  often  be  very 
cold  even  when  the  sun's  rays  are  passing  through  it  to 
warm  the  earth,  and  anyway,  there  is  no  air  at  all 
beyond  a  few  miles  from  the  earth.  We  will  only 
mention  here  that  the  process  by  which  it  travels  is 
called  radiation,  but  the  study  of  radiation  and  radiant 
heat  will  not  come  within  the  compass  of  these  lessons. 
Suffice  it  to  say  that  radiation  is  a  wave-motion,  trans- 
mitted through  an  extremely  elastic  and  subtle  medium, 
that  fills  all  space  and  pervades  all  substances,  called 
the  luminiferous  ether.*  This  "  light-bearing "  ether  is, 
in  fact,  the  same  medium  that  transmits  light  to  our  eyes, 
and  radiant  heat  may  be  called  invisible  light;  for  it 
travels  with  the  enormous  velocity  of  light,  and  obeys 
all  the  laws  of  light,  some  of  which  we  must  proceed  to 
study  in  the  next  chapter. 

*  The  young  reader  must  not  confound  this  word  with  the  liquid 
ether  sold  by  chemists.  The  luminiferous  ether  cannot  be  weighed, 
nor  detected  in  any  way  by  the  senses,  nor  removed  from  any  space  ; 
its  existence  is  assumed  for  good  reasons,  by  scientific  men,  and  its 
properties  are  only  inferred. 


258  THE  FORCES  OF  XATCXE. 


CHAPTER   XVII. 


Now,  let  us  learn  a  little  about  light. 

If  we  go  at  night  into  a  dark  room  we  can  see  nothing 
at  all ;  but  if  we  light  a  candle  we  can  instantly  see  the 
things  in  the  room.  What  is  it  then  that  happens  when 
the  candle  is  lighted  ?  We  will  not  ask  at  first  what 
causes  the  light,  nor  what  the  light  is;  but  only  where 
it  is.  It  is  in  the  candle  flame  certainly  ;  but  instead  of 
staying  only  in  the  flame  the  light  pours  out  in  all 
directions.  Some  of  it  comes  to  our  eyes,  and  then  we 
see  the  candle;  the  light,  whatever  it  is,  brings  us  the 
knowledge  of  the  candle  though  it  is  at  a  distance 
from  us. 

But  there  is  a  book  lying  on  the  table  by  the  candle. 
We  can  see  the  book  too ;  does  light  come  from  that 
to  our  eyes  to  bring  us  the  knowledge  of  it  ?  Yes — until 
the  candle  was  lighted  nothing  came  from  the  book ;  but 
some  of  the  light  that  comes  from  the  candle  strikes 
against  the  book,  and  then,  bounding  back  from  it,  is 
scattered  in  all  directions ;  some  of  this  scattered  light 
comes  to  our  eyes,  bringing  with  it  the  knowledge,  or 
the  picture,  of  the  book.  We  say  the  light  is  scattered, 


LUMINOUS  BODIES.  259 

or  irregularly  reflected,  from  the  book.  Though  it  came 
out  first  from  the  candle,  this  light  does  not  bring  the 
picture  of  the  candle,  but  of  the  book,  which  was  the 
last  thing  it  struck  against. 

Suppose  we  take  the  candle  out-of-doors  on  a  still  dark 
night  to  light  us  in  walking.  As  long  as  we  walk  with 
it  between  houses  and  walls,  some  of  the  candle-light  is 
thrown  back  from  them,  and  though  it  is  not  very  bright, 
yet  we  can  see  pretty  well,  and  there  seems  to  be  some 
light  round  us  ;  if  we  walk  beyond  the  houses  between 
trees  and  hedges  they  will  still  throw  back  a  little  light ; 
but  if  these  come  to  an  end,  and  we  walk  over  a  bare 
common  or  down,  it  becomes  much  darker,  and  we  feel 
as  if  we  and  the  candle  were  alone  in  the  dark.  Of  the 
light  now  around  us  we  only  know  of  a  little  which  comes 
straight  to  us,  making  us  see  the  candle,  and  of  a  little 
which  is  reflected  from  the  ground ;  all  the  rest  pours  away 
into  the  darkness.  But  if  some  one  meets  us  and  stands 
near  us,  there  will  again  be  something  to  send  back 
light,  and  it  will  be  less  dark,  especially  if  the  person  is 
dressed  in  grey  or  white  clothes.  There  was  just  the 
same  quantity  of  light  coming  out  of  the  candle  all  the 
time,  but  we  could  see  very  little  until  the  light  fell  on 
something  which  could  scatter  the  rays  back  to  our 
eyes. 

Luminous  Bodies. — The  candle  flame  is  what  we 
call  self-luminous ;  that  is,  it  gives  out  the  light  by 
which  it  is  seen.  The  sun  is  a  luminous  body ;  so  are 
most  of  the  stars,  and  the  electric  spark,  and  red  hot 
coals  and  some  other  things — we  see  them  by  their  own 
light.  Everything  that  can  be  seen  at  all  must  either 


260  THE  FORCES  OF  NATURE. 

give  out  light  of  its  own,  or  else,  like  the  moon, 
reflect  light  received  from  some  luminous  body,  and  if 
there  are  any  substances  that  neither  give  out  light  nor 
reflect  light,  then  they  can  never  be  seen — they  are 
invisible. 

Transparency,  Translucency,  Opacity. — Take  a 
piece  of  clear  glass  and  hold  it  up  between  your  eyes  and 
the  candle.  You  still  see  the  candle  and  the  flame  quite 
distinctly,  almost  as  if  there  were  nothing  between  it  and 
you.  The  light,  whatever  it  is,  comes  right  through  the 
glass. 

Now,  put  the  flame  inside  a  lamp  shade  of  ground 
glass.  What  can  we  see  ?  The  light  is  still  bright ;  it 
comes  through  the  globe  and  falls  brightly  on  all  the 
objects  round,  only  we  cannot  see  the  actual  flame 
through  the  globe. 

Take  off  the  globe  and  put  the  candle  into  a  dark 
lantern,  closing  the  shutter.  The  light  disappears.  It 
does  not  pass  through  the  tin  case,  and  we  can  only  see 
traces  of  it  at  chinks  or  openings. 

Substances  like  the  clear  glass,  which  allow  us  to  see 
the  forms  of  things  through  them,  are  called  transparent ; 
those  like  the  ground  glass,  through  which  we  can  see 
light,  but  cannot  distinguish  forms,  are  called  translucent : 
while  those  which,  like  the  tin,  shut  out  light  altogether, 
are  said  to  be  opaque. 

The  most  transparent  substance  that  we  know  is  clear 
air.  It  lets  all  the  light  pass  right  through,  and  does  not 
reflect  any  of  it ;  so  that,  as  it  neither  gives  out  light  nor 
reflects  light,  it  is  invisible.  Clear  glass,  crystal,  and 
water,  are  also  transparent,  but  not  perfectly  so.  They 


REFLECTED  LIGHT.  26 1 

do  reflect  a  little  of  the  light  from  their  own  surfaces, 
and  as  this  reflected  light  brings  a  picture  of  them  they 
are  not  quite  invisible,  though  the  greater  part  of  the 
light  passes  through  them,  carrying  on  the  pictures  of  the 
objects  from  which  it  came  before.  So,  then,  by  the  light 
which  they  turn  back  and  reflect,  we  can  see  them,  and 
by  the  light  which  they  allow  to  pass  we  can  see  through 
them. 

We  can  find  substances  of  many  different  degrees  of 
transparency  and  translucency ;  different  kinds  of  glass, 
white  or  coloured,  oils  and  other  liquids,  oiled  paper, 
celluloid,  etc. ;  and  some  we  may  call  half-translucent, 
like  rich-coloured  jewels,  which  seem  to  let  us  see  a  little 
way  into  them,  though  not  right  through  them.  Many 
things  also  are  transparent  if  we  can  get  them  in  thin 
enough  slices,  while  thicker  plates  of  the  same  are 
only  translucent,  and  still  greater  thicknesses  are  quite 
opaque. 

Reflected  Light. — We  saw  just  now  that  light  falling 
on  glass  was  divided,  part  of  it  being  turned  back  or 
reflected  from  the  surface  and  part  passing  through ;  and 
light  always  is  divided,  at  the  surface  of  every  visible 
object.  When  the  candle-light  falls  on  a  book  on  the 
table,  the  book  does  not  reflect  all  the  light  it  receives ; 
it  reflects  some,  or  it  could  not  be  seen.  If  a  piece  of 
glass  lies  on  the  table  beside  it,  this  also  reflects  some  of 
the  light  so  that  it  can  be  seen  ;  but  a  good  deal  passes 
through  to  the  table  beneath  it  and  lights  that  up  too. 
In  the  case  of  the  glass  the  part  of  the  light  that  is  not 
reflected  is  said  to  be  transmitted,  or  passed  through  ; 
but  in  the  book,  and  in  all  opaque  objects,  that  part  of 


262  THE  FORCES  OF  MATURE. 

the  light  that  is  not  reflected  is  said  to  be  absoi'bcd — it  is 
lost  to  sight. 

Now,  try  and  observe  more  closely  and  carefully  still, 
and  we  shall  find  that  even  the  reflected  part  of  the  light 
is  divided  in  two  again.  Lay  a  common  red  pencil  on 
the  table  where  the  light  can  fall  brightly  on  it,  and 
looking  at  it  attentively  you  will  see  a  narrow  line  of 
white  light  along  its  whole  length.  If  you  do  not  see 
this  well  at  first,  move  the  pencil  about  a  little  till  you 
find  a  position  where  the  line  is  quite  bright  and  sharp. 
On  each  side  of  this  white  line  stretches  the  red  surface 
of  the  pencil.  Here  you  see  that  the  light  which  falls 
upon  the  pencil  is  reflected  by  it  in  two  different  ways — 
a  narrow  strip  of  white  light  and  a  wider  band  of  red  light. 

However  solid  any  object  may  seem  to  us  to  be,  its 
minute  particles  or  molecules  are  not  really  quite  close 
together;  but  there  is  a  little,  a  very  little,  distance 
between  them,  and  each  particle  has  surfaces  of  its  own. 
When  the  light  first  strikes  the  outer  surface  of  an  object 
part  of  it  glances  off  immediately,  being  reflected  as 
white  light ;  and  the  smoother  and  more  polished  the 
surface,  the  brighter  and  more  dazzling  is  this  surface 
reflexion,  as  we  may  see  if  a  silver  spoon  or  a  looking- 
glass  is  set  in  the  sunshine.  The  white  line  on  the  pencil 
is  this  first  or  surface  reflexion,  which  painters  call  the 
high  light. 

But  part  of  the  light  gets  in  among  the  particles,  and 
is  reflected  backwards  and  forwards  among  their  in- 
numerable surfaces,  and  here  it  goes  through  a  sort 
of  sifting  before  it  comes  back  to  our  eyes.  Let  us  try 
to  understand  this. 


COLOUR.  263 

Colour. — What  we  call  white  light  is  really  compound, 
made  up  of  the  many  brilliant  coloured  rays  which  we 
see  in  a  rainbow,  and  the  particles  of  objects  select  and 
choose  among  these  coloured  rays,  reflecting  some  and 
absorbing  others.  Our  pencil  appears  red  because  when 
the  light  enters  among  its  particles  they  absorb  all  the 
other  colours  and  reflect  only  the  red.  Roses  and  straw- 
berries look  red  for  the  same  reason ;  but  in  their  leaves, 
on  the  other  hand,  the  red  rays  are  absorbed  and  green 
light  is  returned  to  our  eyes.  And  in  the  same  manner 
everything  is  at  work  dividing  up  the  rays  of  light,  and 
selecting  some  to  reflect  and  some  to  absorb.  A  white 
object  reflects  an  equal  proportion  of  all  the  colours  in 
light;  so  do  grey  ones,  but  the  whole  amount  of  light 
reflected  by  them  is  smaller,  becoming  less  and  less  as 
the  grey  gets  darker,  until  at  last  a  perfectly  black  object, 
in  its  blackest  or  shadowed  part,  reflects  none  of  the 
colours. 

The  red  rays  reach  us  at  the  same  moment  from  every 
part  of  the  space  occupied  by  the  pencil,  and  tell  us  that 
there  is  a  long,  narrow,  straight,  red  thing  on  the  table. 
And  the  rays  also  give  several  other  particulars  about 
it.  The  red  light  being  much  darker  on  one  side,  and 
getting  gradually  lighter  to  the  other  side,  makes  us 
perceive  that  the  object  is  rounded ;  and  finally  the 
brightness  and  sharp  definition  of  the  white  line  tell 
us  that  it  is  also  polished.  The  part  of  the  pencil  that 
has  been  cut  is  not  polished ;  the  white  line  is  not  to  be 
seen  there,  though  it  may  probably  be  found  again  on 
the  black  lead  point. 

Now,  this  is  what  we  mean  by  the  light  bringing  us  a 


264  THE   FORCES   OF  NATURE. 

picture  of  the  object  which  reflects  it.  Bundles  or  sheaves 
of  rays  come  from  every  part  of  the  object,  so  showing 
its  shape ;  the  choice  of  the  particles  among  the  coloured 
rays  shows  us  its  colour;  and  delicate  little  variations 
of  light  and  shade  and  brightness  in  different  parts  give 
us  all  details  about  its  surface.  The  picture  of  an  object, 
therefore,  is  only  brought  by  the  rays  that  have  entered 
among  its  particles,  while  the  mere  white  surface  reflexions 
pass  on,  having  indeed  the  directions  in  which  they  are 
travelling  altered  by  the  reflecting  surface,  but  still 
carrying  with  them  the  picture  of  the  thing  from  which 
they  came  before. 

We  can  see  this  if  we  put  beside  the  pencil  a  smooth 
glass  ink-bottle  with  ink  in  it,  taking  care  that  its  outside 
is  clean  and  bright.  Its  high  light,  or  surface  reflexion, 
is  a  distinct  white  spot,  which  proves,  on  looking  closely, 
to  be  a  tiny  picture  of  the  window  through  which  the 
light  comes.  The  surface  reflexion,  you  see,  brings  no 
picture  of  the  ink-bottle,  but  only  carries  on  the  picture 
of  the  window;  and  it  is  much  more  distinct  on  the' ink- 
bottle  than  on  the  pencil,  because  the  glass  is  more  highly 
polished. 

In  the  same  way  it  is  by  means  of  the  first  or  surface 
reflexion  that  we  see  our  image  in  a  looking-glass,  while 
the  second  reflexion,  when  the  light  has  entered  among 
the  particles,  enables  us  to  see  the  mirror  itself. 

The  surface  reflexions  (which  are  best,  seen  in  mirrors) 
always  follow  a  certain  regular  plan  as  to  the  directions 
in  which  they  travel. 

Regular  Reflexion. — Stand  right  in  front  of  a 
looking-glass,  and  you  can  see  yourself  in  it;  the  light 


REGULAR   REFLEXIOX.  265 

carrying  the  image  of  your  face  strikes  straight  upon  the 
glass,  which  reflects  it  straight  back  to  your  eyes;  but 
move  a  few  steps  to  one  side,  and  you  can  no  longer  see 
yourself,  but  only  things  on  the  other  side  of  the  room. 
Look  at  this  figure  of  the  way  in  which  the  light  is 
reflected.  The  line  inn  is  meant  to  represent  a  section 
or  strip  of  a  mirror.  When  you  stand  right  in  front  of 
the  mirror  it  is  as  if  you  stood  at  d ;  then  the  rays  go 
straight  from  your  face  to  the  mirror  and  come  straight 
back ;  but  when  you  move  to  one  side,  as  to  l>,  then  the 
rays  carrying  the  picture  of  your  face  go  to  the  mirror  at 


d 

Diagram  of  Reflexion. 

a,  and  from  there  bound  away  to  the  other  side,  and  are 
reflected  towards  c,  while  the  light  from  things  at  c  bounds 
off  the  mirror  towards  you,  so  that  what  you  see  in  the 
mirror  are  all  the  things  in  the  direction  of  c.  Notice 
that  the  lines  from  a  to  £,  and  from  a  to  c,  are  just  the 
same  inclination  to  the  line  ad,  only  on  opposite  sides  of 
it.  The  picture  would  serve  as  well  for  an  illustration  of 
tennis  balls  rebounding  from  a  wall  ^s  for  rays  of  light, 
for  a  ball  hit  from  b  to  a  would  bound  oft"  towards  c,  just 
as  the  light  does. 

We  will  make  an  experiment  to  show  the  path  of  the 


266  THE  FORCES   OF  NATURE. 

reflected  rays.  Take  a  box  with  straight  sides  and  a 
glass  lid,  paint  it  all  black  inside,  and  lay  it  on  its  side 
so  that  the  glass  be- 
comes the  front  wall. 
Or  it  will  do  as  well 
to  lay  on  its  side  a 
common  box  without  a 


Experiment  to  show  law  of  Reflex 


fl 


glass  to  close  in  the  front.  Lay  a  flat  piece  of  looking- 
glass,  or  of  smooth  bright  metal,  in  the  bottom  of  the 
box  as  it  lies  on  the  table,  at  a,  in  the  picture,  and  make 
a  small  hole  near  the  top  of  one  end,  as  at  b,  for  a 
sunbeam  to  shine  in  through.  If  you  hold  the  box  in 
the  sunshine  so  that  a  sunbeam  can  come  through  b 
and  fall  upon  the  mirror,  it  will  be  reflected  up  again 
towards  the  other  side  of  the  box,  and  if  the  box  is 
arranged  so  that  the  sunbeam  strikes  the  mirror  just  in 
the  middle,  as  at  a,  then  the  bright  reflected  spot  will  be 
at  c,  opposite  to  b  and  at  exactly  the  same  height.  As 
long  as  there  is  only  clear  air  in  the  box  the  path  of  the 
rays  cannot  be  seen,  but  if  we  fill  the  box  with  smoke,  by 
setting  fire  to  a  bit  of  brown  paper  and  holding  it  for  a 
moment  in  the  box,  which  must  be  quickly  closed  when 
the  paper  is  taken  out,  then  the  path  of  the  rays  will  be 
traced  out  on  the  smoke,  and  we  shall  see  them  following 
the  dotted  lines  on  the  figure.  In  the  picture  there  is 
a  line  drawn  upright,  ad,  from  the  spot  where  the  light 
falls  on  the  mirror,  and  the  two  lines  traced  by  the  ray 
of  light  are  equally  inclined  to  this  central  line,  only 
on  opposite  sides  of  it.*  If  we  now  altered  the  position 
*  Both  this  and  the  next  experiment  require  to  be  tried  in 


REFRACTION. 


267 


of  the  hole,  b,  we  should  find  the  same  law  holding  good. 
At  whatever  slant  the  light  falls  on  the  mirror  it  rebounds 
at  precisely  a  similar  slant.  We  express  this  by  saying 
that  the  angle  of  reflexion,  dac,  is  always  equal  to  the 


two   are   always  on 


angle  of  incidence,  dab,  and  the 
opposite  sides  of  the  line  ad,  which 
we  can  draw  for  ourselves  perpen- 
dicular to  the  mirror. 

Refraction. — Now  let  us  look 
at  the  directions  of  rays  of  light 
when  they  are  transmitted,  or  pass- 
ing into  and  through  transparent 
substances.  Take  a  good-sized 
medicine-bottle,  with  flat  sides,  and 
fasten  over  three  sides  of  it  a 
piece  of  black  stuff  to  darken  it, 
but  leaving  a  smooth  flat  side  un- 
covered to  look  in  through,  as 
here  shown.  At  a  cut  in  the  black 
cover  a  narrow  slit  with  sharp 
edges.  Fill  the  bottle  about  half 

full   Of  Water    in  which  a    few  drops    Experiment  to  show  Refraction. 

of  milk  are  mixed  so  as  to  make  it  a  little  cloudy.  Light 
a  paper  match,  and  hold  it  in  the  upper  part  of  the 
bottle  for  a  moment  so  as  to  fill  it  with  smoke ;  then 
withdraw  it  quickly  and  cork  down  the  bottle  tightly  to 
keep  in  the  smoke. 

If  it  is  now  placed  in  the  sunshine  so  that  a  sunbeam 

sunlight.  Lamplight  will  not  serve  unless  special  arrange- 
ments are  made  to  correct  its  divergence,  and  also  to  render  it 
brighter. 


268  THE  FORCES  OF  NATURE. 

can  enter  at  a  and  strike  on  the  surface  of  the  water,"" 
we  can  see  that  the  beam  is  there  divided  in  two,  a  small 
part  being  faintly  reflected  up  again,  but  the  greater  part 
passing  on  into  the  water.  Notice  that  the  sunbeam  is  not 
straight,  but  is  broken  or  bent  just  where  it  touches  the 
water,  so  that  its  direction  in  the  water  is  different  from 
its  direction  in  the  air.  This  change  of  direction  is  called 
refraction,  from  a  Latin  word  meaning  to  break,  and  it 
takes  place  when  rays  of  light  pass  in  a  slanting  direction 
from  one  transparent  substance  into  another  of  different 
density.  Water  is  denser  than  air,  so  that  the  beam  is 
bent  or  refracted  in  passing  from  air  to  water. 

There  is  only  one  position  in  which  light  would  not  be 
refracted  in  going  into  the  water,  and  that  is  if  it  came 
down  the  neck  of  the  bottle  and  struck  straight  on  the 
surface  of  the  water ;  the  beam  would  then  be  perpen- 
dicular, or  at  right  angles,  to  the  surface  of  the  water, 
and  in  this  position  it  would  pass  straight  into  the  water 
without  changing  its  direction. 

It  is  so  important  to  understand  clearly  the  meaning 
of  perpendicular  to  the  surface  that  we  will  illustrate  it  a 
little  further.  Set  the  flat  end  of  a  pencil  against  a  mirror, 
and  look  at  the  pencil  and  its  reflexion.  If  the  pencil  leans 
a  little  to  the  right  the  reflexion  leans  a  little  to  the  right 
too,  and  the  line  that  they  make  together  is  inclined  in  the 
middle,  as  at  />,  on  the  next  page.  So  it  is  if  the  pencil 
leans  in  any  other  direction,  as  at  c ;  but  when  the  pencil 
and  its  reflexion,  from  whatever  point  they  are  looked  at, 
make  an  unbroken  straight  line  together,  as  at  a,  then  the 

*  By  means  of  a  little  mirror  the  beam  can  be  made  to  enter  at  a 
without  tiltinsr  the  bottle. 


APPARENT  PLACE   OF  OBJECTS. 


269 


pencil  is  perpendicular  to  the  surface  of  the  mirror. 
When  the  mirror  is  lying  quite  flat  the  pencil  will  be 
standing  quite  upright ;  but  whatever  position  the  mirror 
may  be  in,  the  perpendicular  to  its  surface  can  always 
be  found  by  the  same  method.  You  see  there  is  only 
one  direction  in  which  the  pencil  can  point  when  it  is 
perpendicular  to  the  surface ;  if  (with  one  end  still  touch- 
ing the  mirror)  it  points  in  any  other  direction,  it  is  said 
to  be  oblique  to  the  surface — less  oblique  when  it  is  not 
far  from  the  perpendicular  position,  more  oblique  if  it  leans 

A 


Pencil  reflected  in  Mirror. 

more  to  one  side,  as  at  l>,  and  very  oblique  when  it  is 
nearly  lying  down  on  the  mirror.  Look  back  at  p.  267, 
and  you  will  see  that  the  sunbeam  that  entered  the  bottle 
obliquely  to  the  surface  of  the  water,  became  less  oblique 
or  more  perpendicular  to  the  surface  after  it  had  passed 
into  the  water.  Light  is  always  bent  more  towards  the 
perpendicular  direction  in  the  denser  substance. 

Apparent  Place  of  Objects.— We  come  now  to  a 
very  important  point  which  must  be  carefully  remembered. 


2/0 


THE  FORCES   OF  NATURE. 


Light,  we  know,  carries  with  it  pictures  or  images  of 
objects ;  but  if  the  rays  of  light  bringing  these  images  to 
our  eyes  have  rebounded,  or  been  bent  during  their 
journey  (either  by  reflexion  or  by  refraction),  where 
shall  we  see  the  image?  The  image  always  appears  to 
be  in  the  direction  frotn  ivhich  the  rays  came  last. 

Stand  again  in  front  of  the  looking-glass,  inn,  not  right 

in  the  middle,  but  as  at  c,  in  the  picture,  and  put  a  candle 

at  b,  and  an   image  of 

£JYV,  the  candle  will  be  seen 

at  e,  apparently  behind 

^^  the  glass,  or,  as  we  say, 

/'//  the  glass.  The  rays 
which  produce  this  im- 
age have  gone  first  from 
b  to  a,  and  then  from  a 
to  f,  so  that  to  any  one 
standing  at  c  the  image 
is  seen  along  the  line 
fa,  that  is,  in  the  direc- 
tion from  which  the  rays 
came  last.  In  fact,  the  image  appears  to  be  as  far  behind 
the  mirror  as  the  object  really  is  in  front  of  it. 

Just  in  the  same  way  when  the  rays  are  bent  by 
refraction,  we  see  the  image  in  the  direction  from  which 
the  refracted  rays  reach  us.  Place  a  shilling  in  the 
bottom  of  a  glass  basin  and  pour  in  water  gently  so  as 
not  to  move  the  shilling.  When  looked  at  obliquely 
from  above,  the  apparent  position  of  the  shilling  will 
rise  higher  and  higher  as  the  water  rises  in  the  basin. 
It  will  still  appear  to  rest  on  the  bottom,  because  the 


Apparent  place  of  Reflected 
Object. 


A   SIMPLE  EXPERIMENT. 


271 


apparent  place  of  the  bottom  of  the  basin  is  equally 
raised  by  the  refraction ;  but  if  the  eye  is  so  placed 
that  the  edge  of  the  basin,  when  empty,  just  hides  the 
shilling,  the  appearance  of  the  shilling  will  rise  into 
sight  on  pouring  in  the  water.  We  have  seen  that  a 
ray  falling  obliquely  on  water,  as  a  b  (see  picture),  will  be 
refracted  towards  c,  but  it  is  equally  true  that  if  there  is 
an  object  at  c,  some  of  the  rays  bringing  its  picture, 
will  travel  up  through  the  water  to  b,  and  will  there  be 
refracted  in  the  direction  b  a.  If  these  rays  are  re- 
ceived by  an  eye  at  a,  where  will  the  object  at  c  appear 


Apparent  place  of  Coin  altered  by  Refraction. 

to  be  ?  It  will  appear  to  be  in  the  direction  along  which 
the  rays  came  last,  and  consequently  will  be  seen  along 
the  line  ab,  at  about  d.  As  long  as  there  was  no  water 
in  the  basin,  the  shilling  at  c  could  not  be  seen  because 
the  edge  of  the  basin  cuts  off  the  direct  rays  from  c 
to  a,  but  the  addition  of  the  water  has  enabled  us  to 
see  over  the  edge,  without  raising  the  eye  to  c. 

For  the  same  reason  a  stick  plunged  obliquely  into 
water  appears  bent.      The  rays  bringing  the  image  of 


2/2 


THE  FORCES   OF  NATURE. 


the  end  of  the  stick  that  is  under  water  (that  is,  at  c  in 
the  picture  below)  travel  in  the  direction  c  b ;  at  b  they 
are  refracted  into  the  direction  b  a,  so  that  the  eye  at 
a  sees  the  end  of  the  stick  along  the  line  a  b,  and  the 
point  of  it  appears  to  be  at  d,  and  so  with  every  other 
portion  of  the  stick  that  is  under  water.  Similar  reason- 
ing explains  how  every  portion  of  the  stick  that  is  under 
water  (from  c  to  c)  appears  displaced  into  the  position 


Refracted  Image  of  Stick  in  Water. 

c  d>  when  viewed  by  the  eye  at  a.  In  like  manner  the 
apparent  place  of  the  bottom  of  the  vessel  is  also  raised. 
Proportion  of  Light  reflected. — In  our  water- 
bottle  (p.  247),  we  saw  that  very  little  of  the  light 
was  reflected  from  the  surface  of  the  water,  most  of  it 
being  refracted ;  but  the  quantity  of  light  reflected  or 
refracted  depends  on  the  direction  in  which  the  light 
strikes  the  water.  Place  a  sheet  of  smooth,  white 
writing-paper  on  the  table  between  you  and  a  candle, 
and  gradually  raising  it  to  the  height  of  your  eye,  notice 


EFFECTS  OF  REFRACTIOX. 


273 


how  much  brighter  the  reflected  light  becomes.  When 
looked  at  very  obliquely,  an  image  of  the  flame  may  be 
seen  reflected  in  the  paper.  So  when  light  falls  per- 
pendicularly upon  water  only  one-fiftieth  part  of  it  is 
reflected,  but  as  the  beam  falls  more  obliquely  more  and 
more  of  it  is  reflected,  till  the  reflected  part  is  equal  to 
three-quarters  of  the  whole  beam.  Just  the  same  kind 
of  variation  takes  place  with  other  reflecting  surfaces. 

Effects    of    Refraction. — It    would    be    very    in- 
teresting to  show  the  effects  produced  by  causing  beams 


of  light  to  pass  through  transparent  substances  of  certain 
definite  shapes.  We  should  see,  in  one  case,  that 
ordinary  white  light  passing  through  a  three-sided  piece 
of  glass,  called  a  prism,  may  emerge  divided  into  all 
its  beautiful  colours,  the  colours  of  the  rainbow ;  while, 
by  the  passage  of  light  through  differently  shaped  and 
arranged  lenses,  objects  can  be  made  to  look  larger  or 
smaller,  farther  off  or  nearer  than  they  really  are.  All 
these  effects  are  produced  by  refraction. 

The  next  diagram  shows  how  rays  of  light,  starting 
from  a  point,/,  say  a  candle  flame,  diverge  in  all  directions, 


274 


THE  FORCES  OF  NATURE. 


and  then  by  the  "double  convex"  lens  are  made  to 
converge  at  a  point,  /'.  The  converse  would  take 
place  if  the  candle  were  placed  at  /'.  The  two  points 
/and/'  are  called  conjugate  foci  of  the  lens.  If  the  rays 
fall  on  the  lens  from  a  very  distant  source  of  light,  such 
as  the  sun,  the  focus  to  which  the  rays  would  be  bent 


Refraction  of  light  by  a  convex  lens. 

is  then  called  the  principal  focus,  as  the  rays  falling  on 
the  lens  from  a  very  distant  light,  are  practically  parallel. 
If  now  the  source  of  light  is  put  at  the  place  where  the 
principal  focus,  F,  would  be,  then  the  rays  passing  through 
the  lens  emerge  parallel  to  one  another.  If  the  candle 
be  placed  between /and  F,  the  rays,  after  passing  through 
the  lens,  would  converge  to  some  point  more  distant 
from  the  lens  than/'. 
C 


In  the  case  of  a  magic  lantern  the  slide  or  object  is 
placed  in  this  last  position,  as  at  A  B  in  this  picture; 
there  is  thus  formed,  after  the  rays  have  traversed  the 


VELOCITY  OF  LIGHT.  2/5 

lens  C  D,  a  distant,  enlarged  and  inverted  picture,  A'  B'. 
The  rays  from  the  point  B  are,  you  see,  so  refracted  as 
to  form  an  image  at  B',  the  rays  from  A  likewise  form 
an  image  at  A',  and  so  on  with  all  the  intervening  points 
of  the  object  A  B.  To  get  the  picture  the  right  way 
up,  the  lantern  slide,  corresponding  to  A  B,  must  there- 
fore be  upside  down.  If  the  object  were  at  A'  B'  the 
picture,  or  image,  would  be  at  A  B ;  this  is  similar  to 
what  occurs  in  a  camera  obscura,  or  a  photographic 
camera,  or  the  eye,  a  smaller  inverted  image  of  outside 
objects  is  seen  at  A  B,  where  the  photographic  plate,  or 
the  retina  in  the  case  of  the  eye,  is  placed. 

Velocity  of  Light. — The  only  other  point  that 
can  be  mentioned  here  is  the  enormous  speed  at  which 
Light  travels — a  rate  of  not  less  than  186,000  miles  a 
second.  Here  on  the  surface  of  the  earth  it  is  practi- 
cally instantaneous.  We  can  see  the  light  of  a  match 
the  instant  it  is  struck ;  not  an  instant  is  wasted  while 
the  light  is  passing  from  the  spark  to  our  eyes. 

But  though  light  travels  at  this  extraordinary  speed, 
yet  the  distances  of  the  heavenly  bodies  from  us  are 
so  great  that  light  actually  takes  eight  and  a  quarter 
minutes  in  reaching  us  from  the  sun ;  about  five  hours 
in  coming  from  the  planet  Neptune;  not  less  than  3^ 
years  from  the  nearest  fixed  star ;  and  probably  centuries 
in  coming  from  the  nearest  nebulae. 

Light  is  the  only  messenger  conveying  to  our  bodily 
senses  communications  from  these  vast  distances,  so 
that  our  knowledge  of  the  stars  depends  entirely  on  the 
information  which  it  brings. 


2/6  THE  FORCES  OF  NATURE. 


CHAPTER   XVIII. 


WHILE  Light  in  its  swift  journeys  brings  us  intelligence 
alike  from  far  and  near,  we  have,  with  our  nearer  sur- 
roundings only,  another  means  of  communication  in 
Sound,  the  sound  of  voices,  of  music,  and  of  all  kinds  of 
noise ;  and  a  thunderstorm  gives  us  a  good  opportunity 
of  comparing  the  relative  speed  of  Light  and  Sound. 

Velocity  of  Sound. — When  there  is  a  storm  close 
to  us  we  see  the  lightning  flash  and  hear  the  thunder 
clap  at  the  same  moment ;  but  when  the  storm  is  further 
off  we  see  the  lightning  first,  and  then  have  to  wait  for 
the  sound  of  the  thunder.  What  is  the  reason  for  this 
difference  ?  The  lightning  and  thunder  really  take  place 
at  the  same  time ;  but  while  the  Light  reaches  us  instantly, 
travelling  at  the  rate  of  186,000  miles  in  a  second,  the 
Sound  lags  behind,  and  we  have  to  wait  while  it  is 
coming.  Through  air  at  an  ordinary  temperature  it 
only  comes  at  the  rate  of  1120  feet  a  second,  and  by 
counting  the  number  of  seconds  which  elapse  before 
it  arrives,  we  can  tell  how  many  times  1120  feet  the 
sound  has  travelled,  and  so  ascertain  the  distance  of  the 
storm. 


VELOCITY  OF  SOUND.  277 

In  the  same  way,  if  we  watch  any  one  firing  a  gun 
some  way  off,  we  can  see  the  flash  and  the  smoke  before 
the  report  reaches  us;  and  a  quaint  effect  is  produced 
by  regular  hammering  or  wood-chopping  at  a  little 
distance,  the  sight  and  the  sound  of  the  blows  coming 
not  together  but  by  turns. 

But  the  velocity  of  sound  varies  according  to  the 
substance  through  which  it  is  passing.  Through  water 
it  conies  four  times  as  fast  as  through  air,  and  through 
most  solids  faster  still,  the  speed  in  iron  being  about 
fifteen  times  as  great  as  in  air.  Put  your  ear  against  a 


A  toy  mechanical  telephone. 

telegraph-post  while  some  one  hits  the  next  post  with  a 
stick,  and  you  will  hear  the  sound  of  the  blow  twice,  the 
first  report  running  very  quickly  through  the  telegraph 
wire  and  the  wood,  while  the  second  is  travelling  more 
slowly  straight  through  the  air. 

It  is  easy  to  make  a  toy  telephone  which  will  carry 
sound  a  long  way.  Take  two  empty  boxes  of  thin  wood 
without  covers  (cigar  boxes  do  well),  bore  a  hole  in  the 
bottom  of  each,  and  pass  through  each  of  them  one 
end  of  a  long  string,  or  still  better,  of  a  wire,  say  a  long 
bell-wire ;  now  knot  the  ends,  and  take  the  boxes  as  far 


2/8  THE  FORCES  OF  NATURE. 

apart  as  the  wire  will  allow.'"'  The  wire  should  be  kept 
tightly  stretched,  but  it  need  not  be  kept  straight  all  the 
way ;  you  can  bend  it  round  a  corner  without  any  harm. 
Turn  the  bottoms  of  the  boxes  towards  each  other  ;  and 
then  if  you  place  your  ear  against  one  of  them  you  can 
hear  any  tap  that  is  made  upon  the  other,  by  the  sound 
travelling  through  the  wire.  If  a  tuning-fork  is  struck 
and  made  to  sound  near  one  box  it  will  be  distinctly 
heard  through  to  the  other,  and  if  you  whisper  into  one 
box  your  whisper  will  be  heard  at  the  other.  Neither 
tuning-fork  nor  whisper  can  be  heard  through  the  air, 
if  your  distance  apart  is  sufficient,  because  the  sound 
waves  spread  in  all  directions  through  the  air  (unless 
confined  by  a  speaking  tube),  and  so  their  loudness 
rapidly  fades  away.  The  wire,  or  stretched  twine,  con- 
veys or  conducts  the  sound  along  itself,  and  so  prevents 
its  decay  at  moderate  distances.  This  is  the  principle 
of  the  mechanical  telephone  which  the  writer  has  used 
for  conversation  between  two  houses  a  mile  apart,  even 
the  faintest  whisper  at  one  end  being  heard  at  the  other. 

Connexion  of  Sound  and  Motion. — Whatever  is 
producing  sound  is  in  motion.  Strike  a  tuning-fork 
sharply  and  hold  it  in  your  hand,  and  you  can  feel  its 
motion  all  the  time  the  sound  continues.  Sometimes  we 
can  actually  see  the  ends  moving,  and  by  the  following 
simple  plan  we  can  certainly  show  the  motion. 

With  a  little  morsel  of  wax  fasten  on  to  each  prong  of 
a  tuning-fork  a  small  bright  silvered  bead.  (One  would 

*  The  picture  shows  a  ball  of  twine  that  is  intended  to  be  stretched 
tightly  between  each  box  ;  but  you  will  find  it  easier  to  take  a  shorter 
length  than  this.  The  electric  telephone  is  of  course  a  different  thing. 


SOUND  AND  MOTION.  2/9 

do,  but  something  to  balance  it  must  be  put  on  the  other 
that  the  weight  may  be  the  same.)  Rest  the  end  of  the 
fork  on  the  table  where  the  sun  can  shine  on  it,  and 
notice  where  the  bright  reflexion  falls  from  one  of  the 
beads ;  if  it  falls  in  a  shadowed  place  it  will  be  more 
visible.  Then  strike  the  fork  and  rest  it  as  before,  and 
you  will  see  the  spot  of  reflected  light  lengthened  out 
into  a  bright  line  by  the  rapid  shaking  or  vibrating  of  the 
bead  backwards  and  forwards. 

The  following  experiment  is  perhaps  easier  for  you  to 
manage.  Instead  of  fastening  the  bead  to  the  fork,  hang 
up  the  bead  by  a  piece  of  thread ;  or  a  little  ball  of  sealing- 
wax  will  do  as  well  as  the  bead ;  now  strike  the  tuning- 
fork  and  bring  it  carefully  to  the  bead ;  directly  the  tip 
of  the  fork  touches  the  bead,  away  the  latter  is  dashed, 
and  as  it  falls  back  gets  another  blow  from  the  vibrating 
fork,  and  so  on  till  the  tuning-fork  ceases  to  sound,  and 
then  the  bead  hangs  motionless. 

Here  is  another  pretty  experiment.  Fill  a  round 
glass  finger-bowl  about  half  full  of  water,  and  set  it  on  a 
tablecloth  or  something  soft.  Wet  your  finger  and  draw 
it  with  a  firm  but  light  pressure  round  and  round  the 
rim,  until  the  glass  gives  out  a  clear  musical  note. 
Continue  the  movement,  and  presently  you  may  see 
a  corresponding  movement  in  the  water,  which  rises  in 
a  tiny  wave  of  exquisite  ripplings,  and  follows  the  course 
of  the  finger  round  the  glass.  Here  the  glass  is  thrown 
into  rapid  vibration  (or  movement  of  its  substance  back- 
wards and  forwards),  and  the  motion  being  communicated 
to  the  water  shows  itself  in  visible  waves. 

These  have  been  examples   of  small,  rapid,  delicate 


280  THE  FORCES  OF  NATURE. 

movements  with  rather  soft  sounds;  but  very  loud 
sounds  imply  much  more  violent  movements.  Any  one 
who  has  heard  the  deep  pedal  notes  of  a  large  and  power- 
ful church  organ  knows  how  they  will  sometimes  shake 
the  whole  building,  and  the  hearer  feels  them  as  a  great 
throbbing  all  through  him ;  while  the  violent  shaking  of 
the  air  that  is  produced  by  cannon  firing  or  by  blasting 
is  sometimes  sufficient  to  break  windows  in  the  neighbour- 
hood. 

Vibratory  Motion. — We  saw  that  the  ends  of  the 
tuning-fork  were  moving  rapidly  backwards  and  forwards 
all  the  time  it  sounded,  that  the  glass  of  the  finger-bowl 
and  the  rippling  water  were  vibrating  to  and  fro,  that  the 
organ  notes  made  a  continuous  throbbing.  Even  the 
cannon  firing  and  the  blasting  do  not  end  in  single  motions, 
but  set  the  air  rocking  violently.  And  so  it  always  is. 
The  motion  which  produces  sound  is  never  a  single  motion, 
but  always  consists  of  vibration  or  swinging  backwards 
and  forwards  of  the  sounding  body ;  not  an  imperceptible 
motion  of  its  invisible  particles  or  molecules,  as  is  the 
case  with  a  luminous  or  a  hot  body,  but  a  vibration  you 
can  feel,  or  that  can  be  made  perceptible  by  simple 
means.  Moreover,  the  sounding  body  vibrates  as  a 
whole,  or  in  a  few  aliquot  parts,  comparatively  slowly 
(see  p.  282),  whereas  the  molecules  of  a  luminous  or  a 
hot  body  vibrate  with  inconceivable  rapidity,  millions 
of  millions  of  times  in  every  second,  and  set  going  waves 
in  the  ether  (p.  257),  which  come  to  us  as  light  or  radiant 
heat.  The  sounding  body  produces  waves  ///  the  air, 
which  travel  vastly  slower  (p.  276),  and  on  reaching  our 
ears  give  rise  to  the  sensation  of  sound. 


AN  AIR  PUMP. 


28l 


But  when  there  is  nothing  to  carry  on  the  waves  sound 
does  not  travel  at  all.  It  can  pass  along  solids,  as  we 
found  with  the  telegraph-post  and  the  toy  telephone ;  it  is 
transmitted  by  liquids — a  man  floating  with  his  ears  under 
water  can  hear  sounds — and  we  know  that  it  comes 
through  the  gases  of  the  air ;  but  in  a  vacuum,  where 
there  is  neither  solid,  liquid,  nor  gaseous  substance  to 
carry  it  on,  all  sound  dies  out. 

Here  is  a  diagram  of  an  air-pump.  You  see  that  the 
piston  (a),  working  up  and  down  in  a  cylinder,  is  arranged 
exactly  like  that  of  the  water-pump  on  p.  227  ;  but  the 
tube  below  (^),  instead  of  dipping  down  into  water, 
passes  into  a  bell  glass  (c),  closely  fitted  upon  a  plate  ; 
so  that  by  working  the  piston  up  and  down  we  can  pump 
all  the  air  out  of  the  glass.  If  a  watch,  or,  still  better, 
a  small,  loud-ticking  American  clock,  is  placed  under 


Diagram  of  air-pump. 

the  bell  glass  (resting  on  a  thick  pad  of  cotton  wool  to 
prevent  the  plate  carrying  the  vibrations),  we  shall  hear 
it  through  the  glass  ticking  away  merrily.  But  on  work- 
ing the  piston  so  as  to  pump  away  the  air,  the  ticking  can 
no  longer  be  heard ;  sound  cannot  cross  a  vacuum. 


282  THE  FORCES   OF  NATURE. 

You  will  have  noticed  that  when  a  tuning-fork  is  held 
in  the  air  very  little  sound  is  heard,  but  when  set  on  a 
table  the  whole  table-top  vibrates  with  it  and  the  sound 
is  much  louder,  because  a  much  larger  surface  is  set  in 
vibration.  So  a  violin  string  stretched  in  the  air  and 
set  vibrating  gives  but  a  very  weak  sound,  but  when 
stretched  upon  the  thin  hollow  violin,  both  the  front 
and  back  of  the  case  and  all  the  air  inside  it  vibrate 
together  and  give  out  a  powerful  sound. 

When  vibrations  are  slow,  they  are  merely  separate 
throbs ;  but  when  they  follow  each  other  with  not  less 
than  a  certain  rate  of  speed,  they  become  audible  as  a 
continuous  sound. 

Musical  Sounds. — If  the  vibrations  are  irregular, 
we  hear  merely  a  noise ;  but  if  they  are  regular — that 
is,  follow  each  other  at  regular  intervals— and  at  the 
same  time  are  sufficiently  rapid,  we  have  a  musical  note. 
The  pitch  or  height  of  the  note  depends  on  the  number 
of  vibrations  in  a  second.  Slower  vibrations  give  a 
deep,  low  note :  when  they  come  faster  the  note  rises 
in  pitch,  and  very  rapid  vibrations  cause  a  high  shrill 
note.  Faster  still  they  cannot  be  heard  at  all ! 

Sixteen  vibrations  in  a  second  make  a  note  about  as 
low  as  can  be  heard  at  all,  and  by  the  word  vibration,  we 
mean  a  complete  swing  to  and  fro ;  double  that  number, 
32,  give  a  note  an  octave  higher;  64  is  an  octave  higher 
again,  and  so  the  notes  rise,  doubling  the  number  of  vibra- 
tions with  every  octave,  until  we  reach  the  acutest,  shrillest 
squeak  that  can  be  heard  at  somewhere  about  30,000 
vibrations  in  a  second,  making  in  all  some  eleven  octaves. 
There  is,  however,  a  good  deal  of  question  as  to  the 


MUSICAL  SOUNDS.  283 

extreme  limits  at  the  top  and  bottom  of  the  range  of 
hearing,  and  there  can  be  no  doubt  that  people  differ  a 
good  deal  in  their  actual  power  of  hearing  very  deep 
or  very  acute  sounds. 

When  old  age  is  coming  on,  and  the  hearing  becomes 
a  little  dull,  the  first  failure  is  in  the  power  of  hearing 
very  shrill  sounds.  A  short  time  since,  a  party  of 
travellers  were  riding  on  mules  over  the  pass  of  the 
Grimsel,  in  Switzerland,  and  an  elderly  gentleman  re- 
marked how  weary  he  was  of  the  dull  thud,  thud,  of 
the  mules'  feet  upon  the  turf;  but  his  younger  com- 
panions could  not  hear  it  on  account  of  the  shrill  noisy 
chirruping  kept  up  by  myriads  of  large  grasshoppers 
beside  the  way.  This  noise,  though  so  loud  to  them 
as  entirely  to  conceal  the  sound  of  the  mules'  tread, 
was  absolutely  unheard  by  the  old  gentleman,  who, 
with  advancing  age,  had  lost  his  former  power  of  hearing 
sounds  so  high  in  the  scale. 

But  whilst  a  good  ear  can  distinguish  sounds  through 
a  range  of  some  1 1  octaves,  no  one  would  call  the  lowest 
and  highest  sounds  musical ; 
in  fact,  the  sounds  which  are 
musically  available  only  range 
from  about  40  to  4000  vibra- 
tions a  second,  that  is,  about 
7  octaves. 

The  note  called  the  middle  C 

on  the  pianoforte  here  shown  has  about  260  vibrations  in 
a  second,  though  it  is  sometimes  placed  a  little  higher 
or  lower  according  to  different  standards  of  pitch.  This 
is  a  useful  central  note  to  remember.  To  compare 


284  THE  FORCES  OF  NATURE. 

the  notes  of  a  scale  any  tone  may  be  chosen  as  a 
keynote.  If  we  take  G,  then  the  keynote  has  384 
vibrations  in  a  second,  the  third  note  above  it  has  480, 
the  third  above  that  again,  or  the  fifth  of  the  scale,  has 
576,  and  the  octave,  as  we  know,  double  the  keynote, 
or  768.  These  four  notes,  keynote,  third,  and  fifth, 
completed  with  the  octave  above,  make  what  is  called 
,  the  common  chord  of  the 

C\  I  key  here  shown,  and  what- 

\j  \        \      r\       ever  keynote  maybe  taken, 

f— A \ — & —  the   number  of  vibrations 

I — I  /t^ ^H 

I '  U & in  the  notes  of  its  common 

chord     always    have    this 
C/  same  fixed   proportion  to 

The  common  chord  of  G.  . 

one  another;   the  third  a 

quarter  more  than  the  keynote,  the  fifth  a  half  more, 
and  the  octave  double  the  keynote ;  this  proportion  is 
as  the  numbers  4,  5,  6,  8.* 

There  is  no  prettier  or  more  interesting  subject  of 
study  than  the  close  relation  between  music  and 
mathematics. 

*  Taking  the  numbers  given  for  the  keynote  of  G,  namely,  384, 
480,  576,  and  768,  and  dividing  each  number  by  96,  you  will  find 
the  proportion  of  4,  5,  6,  8,  as  stated. 


CHAPTER   XIX. 
MAGNETISM. 

IF  you  go  to  a  toy-shop  and  ask  for  a  magnet  (which 
may  be  bought  for  sixpence,  or  one  shilling)  you  will 
receive  a  piece  of  steel  bent  into  the  shape  of  a  long 
horse  shoe.  There  will  be  a  second  small 
piece  of  iron  with  it,  bridging  across  the 
opening  between  the  two  ends.  Pull  off 
this  piece  (which  is  called  the  keeper),  place 
it  on  the  table,  and  bring  the  ends  of  the 
horseshoe  piece  near  it,  when  it  will  be 
attracted,  and  will  stick  quite  firmly  to  it,  , 

*  '      Magnet  and 

requiring  some  considerable  force  to  pull  keeper. 
it  away.  Take  it  off  again,  and  put  on  the  table 
other  small  pieces  of  iron  or  steel — nails,  needles,  or 
anything  you  like — and  you  will  find  them  all  attracted 
in  the  same  way.  The  horse-shoe,  dipped  into  a  box  of 
small  nails,  will  come  out  bristling,  like  a  hedgehog,  with 
nails  sticking  all  over  its  ends.  Any  piece  of  steel  like 
this,  which  will  attract  other  pieces  of  iron,  is  called 
a  magnet,  and  the  property  by  means  of  which  it  acts 
is  called  magnetism. 

Notice  that  the  attraction  of  a  magnet  is  not  of  the 
same  kind  as  that  exercised  by  an  excited  glass  or  wax 


286  THE  FORCES  OF  NATURE. 

rod,  which  we  shall  study  presently  under  the  head  of 
electricity,  for,  while  those  will  attract  any  light  insulated 
object  for  a  moment,  repelling  it  again  as  soon  as  it  is 
touched,  the  magnet  attracts  only  pieces  of  iron,  and 
they  remain  sticking  firmly  to  it.  Try  to  attract  bits  of 
paper  or  bran  by  your  magnet  and  you  will  not  succeed. 
Besides,  the  attractive  power  of  a  rubbed  glass  rod  will 
disappear  at  once  if  it  is  not  insulated,  but  we  can  handle 
a  magnet  freely  without  affecting  its  power  of  attraction. 

Take  a  short  steel  knitting-needle,  and,  laying  it  on 
the  table,  stroke  it  several  times  from  end  to  end  with 
one  end  of  the  horse-shoe  magnet.  It  does  not  matter 
which  end  you  use,  but  you  must  keep  to  the  same 
throughout,  and  must  always  stroke  the  needle  in  the 
same  direction,  never  rubbing  backwards  and  forwards. 
After  this  treatment  you  will  find  that  the  knitting-needle 
has  also  become  a  magnet,  and  will  attract  small  pieces 
of  iron.  A  second,  and,  in  some  ways,  more  convenient 
method  of  making  the  needle  magnetic,  is  this :  hold 
it  in  your  hand,  and  stroke  several  times  from  the  middle 
to  one  end  with  one  end  of  the  magnet,  and  then,  turning 
it  round,  stroke  from  the  middle  to  the  other  end  with 
the  other  end  of  the  magnet. 

Now,  lay  your  magnetic  needle  in  a  loop  of  paper, 
pass  a  thread  through  the  paper,  and  knotting  its  ends 
together,  hang  it  up  to  a  support,  so  that  the  paper  and 
needle  can  swing  freely.  Notice  that  the  needle  takes 
up  a  certain  position  ;  we  may  push  the  end  round  to 
one  side,  but  it  will  return  to  the  same  position  :  we  may 
move  the  support  round,  but  the  needle,  after  swinging  a 
little,  will  always  settle  down  in  the  same  direction  as 


THE  MAGNETIC  POLES. 


287 


before,  and  this  direction  is  very  nearly  due  north  and 
south.  So,  then,  we  have  found  out  that  one  end  of  a 
magnetic  needle,  if  free  to  move,  will  turn  and  point  to 
the  north  and  the  other  to  the  south.  One  end  is  called 
the  North-seeking  pole,  or,  for  short,  the  North  Pole, 
while  the  other  is  the  South-seeking  or  South  Pole. 
Mark  your  magnet  in  some  way,  so  that  you  may  know 


Knitting-needle  magnetized  and  suspended. 

its  north  pole  from  its  south ;  a  dab  of  paint  will  do,  or 
a  tiny  morsel  of  paper  gummed  on. 

Now,  let  us  magnetize  a  second  knitting-needle,  and 
after  testing  and  marking  it  in  the  same  way,  we  will 
balance  it  in  the  paper  loop,  and  then  bring  the  nortli 
pole  of  the  first  needle  near  to  the  north  pole  of  the  second. 
Notice  that  the  end  of  the  needle  moves  away  from  it. 
Bring  the  south  poles  near  each  other,  and  we  find  again 
that  the  south  pole  of  one  magnet  moves  away  from  the 
south  pole  of  the  other.  But  if  we  present  the  north  pole 
of  one  to  the  south  pole  of  the  other,  we  find  that  they 
attract  each  other.  From  this  we  see  that  like  poles  repel 


288  THE  FORCES  OF  XATURE. 

one  another,  and  unlike  poles  attract ;  a  result  which,  as 
we  shall  see  presently,  reminds  us  of  the  repulsion  and 
attraction  between  like  and  unlike  charges  of  electricity. 

Here  is  a  pretty  experiment.  Lay  the  magnets  parallel 
to  each  other  a  little  way  apart  on  the  table,  place  a  sheet 
of  stiff  white  paper  over  them,  and  then  sift  down  upon 
it  some  fine  iron-filings  through  a  small  fine  muslin  bag. 
See  how  curiously  the  filings  arrange  themselves  in 
curved  lines;  they  feel  and  obey  the  attraction  of  the 


Magnetic  curves,  similar  poles  juxtaposed. 


magnets  through  the  paper.  If  we  put  the  south  pole  of 
one  magnet  opposite  the  south  pole  of  the  other,  at 
a  distance  apart  of  about  an  inch,  two  sets  of  curves  are 
formed  which  seem  to  be  independent  of  one  another  ; 
but  if  a  north  pole  is  placed  opposite  a  south  pole,  the 
curves  pass  from  one  magnet  to  the  other.  These 
curved  lines  are  called  lines  of  magnetic  force,  and  the 
space  through  which  they  are  spread  is  called  the  mag- 
netic field.  If  you  like  to  make  these  curves  permanent, 


MAGNETIC  CURVES.  289 

instead  of  the  plain  white  paper  lay  down  a  sheet  that  has 
been  gummed  all  over  and  allowed  to  dry ;  then  when 
the  filings  have  arranged  themselves,  without  moving  the 
paper,  let  some  steam  pass  very  gently  over  the  surface 
(if  the  gum  is  fairly  thick  even  breathing  over  it  may  be 
enough),  and  the  gum  will  soften  for  a  moment  and  dry 
again,  holding  the  filings  in  their  places. 

We  know  that  a  magnet  has  a  north  and  a  south  pole. 


Magnetic  curves,  unlike  poles  juxtaposed. 

Now,  what  would  happen  if  we  broke  it  in  two  through 
the  middle  ?  Should  we  have  one  piece  all  north  pole, 
and  the  other  all  south  ?  No ;  we  find  that  each  piece 
is  a  complete  magnet,  the  broken  ends  becoming  a  south 
pole  to  the  north  pole  half,  and  a  north  pole  to  the  other 
half.  No  matter  into  how  small  fragments  a  magnet  may 
be  broken,  each  will  still  have  north  and  south  poles  of 
its  own  and  be  a  complete  magnet.  It  is  impossible  to 
separate  the  poles  of  a  magnet. 

u 


290  THE  FORCES  OF  NATURE. 

We  have  converted  small  steel  bars  into  magnets  by 
merely  stroking  them  with  a  magnet,  and  now  that  we 
know  the  difference  between  north  and  south  poles  we 
may  notice  that  if  we  stroke  with  the  north  pole  of  the 
magnet,  the  end  last  touched  of  the  new  magnet  will  be 
a  south  pole ;  or  if  we  stroke  with  a  south  pole,  the  end 
last  touched  will  be  a  north  pole. 

But  try  the  same  experiment  with  a  key  or  an  iron 
nail  (made  of  so-called  "soft"  iron).  Stroke  carefully 
and  then  dip  either  point  into  the  iron  filings ;  they  do  not 
stick  to  it.  Touch  the  head  of  the  nail  or  key  with  a 
strong  magnet,  and  they  will  stick  to  it  instantly ;  whilst 
thus  sticking  on,  dip  the  lower  end  of  the  nail  into  iron 
filings;  now  they  fly  to  the  nail,  which  has  become 
magnetized  by  being  near  to  the  magnet,  but  as  soon  as 
the  magnet  is  removed  from  the  nail  the  filings  will  drop 
off  again.  So  it  appears  that  hard  steel  becomes  a  per- 
manent magnet  when  properly  stroked  with  a  magnet,  but 
that  soft  iron  cannot  be  permanently  magnetized  in  this 
way;  it  is  a  magnet  while  the  steel  magnet  is  touching 

it,  but  when  that  is 
taken  away  all  the 
magnetic  power  dis- 
appears. 

There  is  another 

Magnetic  needle.  w  >n       wjjich       a 

piece  of  soft  iron  may  be  converted  into  a  temporary 
magnet,  which  is  by  the  use  of  electricity ;  but  we  shall 
come  to  this  presently. 

The  most  important  use  of  the  small  magnet,  or 
magnetic  needle,  is  in  the  mariner's  compass.  In  this 


THE  MARINER'S   COMPASS.  29! 

a  magnetic  needle  is  balanced  on  an  upright  point,  so 
that  it  can  swing  round  freely;  and  as  it  places  itself 
pointing  nearly  north  and  south,  the  sailor  can  tell  from 
it  in  what  direction  he  is  steering  his  ship.'"  Before  the 
discovery  of  the  compass,  ships  could  rarely  venture  to 
sail  out  of  sight  of  land,  for  though  they  might  be  steered 
by  the  sun  and  stars,  yet  they  were  in  great  danger  of 
going  astray  when  these  were  hidden  by  thick  clouds. 

Magnetism  of  the  earth. — We  said  just  now  the 
compass  needle  points  nearly  north  and  south.  Why 
is  this  ?  The  earth  behaves  as  if  it  were  a  huge  magnet, 
with  its  poles  near  to,  but  not  coinciding  with,  the  geo- 
graphical poles.  As  it  is  to  the  magnetic  pole  the  needle 
points,  this  want  of  coincidence  gives  rise  to  what  is 
called  the  variation  of  the  compass.  The  north  magnetic 
pole  is  in  the  Arctic  region  of  Boothia,  a  place  north  of 
Hudson's  Bay;  the  south  magnetic  pole  has  not  yet 
been  reached.  Now  look  at  a  map,  and  you  will  see 
that  in  Europe  and  the  Atlantic  the  needle  must  point 
west  of  the  true  geographical  north,  whilst  in  the  Pacific, 
etc.,  it  will  point  east  of  the  true  north,  and  on  some 
meridian  between,  the  compass  will  have  no  variation 
or  point  true  north.  Thus  the  variation  of  the  compass 
is  different,  both  in  amount  and  direction,  in  different 
longitudes  on  the  earth's  surface. 

*  In  the  mariner's  compass  a  card,  called  the  compass  card,  is 
fixed  to  the  needle  and  moves  with  it.  This  card  has  its  rim 
divided  into  32  equal  parts,  called  the  points  of  the  compass.  The 
vessel  is  steered  by  keeping  a  certain  line,  corresponding  to  the 
head  of  the  vessel,  opposite  the  right  point  on  the  compass. 


THE  FORCES  OF  NATURE. 


CHAPTER  XX. 
ELECTRICITY. 

EVERY  one  has  heard  of  the  wonders  of  Electricity — of 
the  Telegraph,  by  which  messages  can  be  sent  hundreds 
of  miles  in  shorter  time  than  it  takes  to  say  the  words ; 
of  the  Telephone,  which  enables  a  man  to  speak  to 
another  hundreds  of  miles  away,  and  yet  be  heard  as 
distinctly  as  if  he  were  talking  only  through  a  short 
length  of  pipe;  of  the  bright  Electric  Light;  and 
of  trains,  tramcars,  and  other  vehicles,  worked  by 
Electricity. 

What  this  powerful  agency  is  we  know  not.  We  are 
as  ignorant  of  its  actual  nature  as  we  are  of  the  nature 
of  Gravitation,  the  falling  together  tendency;  and  even 
to  explain  fully  the  way  it  works  would  require  volumes. 
All  we  can  do  here  is  to  learn  by  simple  experiments 
some  of  the  first  things  which  must  be  known  before  we 
can  possibly  understand  more. 

FRICTIONAL  ELECTRICITY. 

Let  us  recur  to  the  little  experiment  mentioned  on 
p.  205.  Tear  up  some  thin  light  paper  into  pieces  about 
half  the  size  of  a  threepenny  piece;  then  take  a  stick 


FRICTIONAL   ELECTRICITY.  293 

of  sealing-wax,  or  some  article  made  of  black  ebonite, 
or,  if  you  like,  the  amber  mouthpiece  of  a  tobacco-pipe, 
rub  it  well  on  your  sleeve  or  some  other  woollen  sub- 
stance, bring  the  end  of  it  near  the  pieces  of  paper,  and 
you  will  see  them  jump  up,  touch  the  rubbed  body,  fall 
off,  jump  up  again,  and  so  on  for  a  considerable  time. 
Now,  instead  of  the  sealing-wax  try  a  glass  rod  rubbed 
with  a  silk  handkerchief,  first  making  both  very  dry  by 
holding  them  in  front  of  the  fire  until  they  are  quite 
hot,  and  we  shall  find  that  the  glass  rod  has  the  same 
power  of  attracting  the  bits  of  paper. 

Sealing-wax  and  glass  rods  in  their  usual  state  have 
no  effect  of  this  kind,  so  that  it  is  plain  that  some 
difference  has  been  made  in  them  by  the  rubbing.  We 
say  that  they  are  electrified,  or  electrically  excited,  or 
charged  with  Electricity.  This  name  is  derived  from 
electron,  the  Greek  word  for  amber,  for  the  ancient 
Greeks  knew  that  a  piece  of  amber  when  rubbed  would 
attract  light  bodies,  and  they  thought  the  rubbing  put 
some  sort  of  life  into  the  amber. 

Conduction. — Notice  that  the  rubber  and  the  rubbed 
body  are  different  substances.  So  far  as  we  know  any 
two  unlike  bodies  rubbing  together  become  electrified ; 
even  the  liquid  metal  mercury  shaken  in  a  dry  glass  gets 
strongly  electrified  by  its  friction  with  the  glass. 

At  first  sight  this  statement  does  not  appear  to  be 
true,  for  when  we  take  a  rod  of  brass  or  any  metal,  rub 
it,  and  bring  it  near  the  pieces  of  paper,  they  are  not 
attracted.  If,  however,  we  attach  the  brass  rod  to  a 
glass  or  ebonite  handle  and  rub  the  brass,  holding  it 
by  the  handle  so  as  not  to  touch  it  with  the  hand,  we 


294  THE  FORCES  OF  NATURE. 

find  that  it  does  now  attract  the  light  particles.  The 
reason  of  this  is,  that  the  electricity  which  is  produced 
on  rubbing  the  metal  was  able  in  the  first  case  to  pass 
along  the  metal  to  the  hand,  from  the  hand  into  the 
body  and  into  the  ground,  and  so  to  escape ;  while,  in 
the  second  case,  the  glass  handle  prevented  it  from 
passing,  so  that  it  remained  on  the  metal  where  it  was 
produced.  We  see  from  this  that  some  substances  will 
allow  electricity  to  pass  through  them  while  others  will 
not ;  that  there  are  good  and  bad  conductors  of 
electricity  as  there  are  of  heat,  and  that  metals  are 
good  conductors,  while  glass,  amber,  ebonite,  etc.,  are 
bad  or  non-conductors.  Fastening  the  brass  rod  to  the 
non-conducting  handle  is  called  insulating  it,  that  is, 
keeping  it  separate  from  anything  to  which  it  might 
transmit  its  electric  charge. 

Doubleness  in  Electricity.— We  will  study  a  little 
more  closely  the  electricity  produced  on  different  bodies. 
Take  two  very  light,  small  objects,  such  as  tiny  balls 
of  pith,  thread  each  on  a  piece  of  fine  silk  thread,  and 
hang  them  from  two  pieces 
of  stout  wire  bent  at  right 
angles,  bending  one  end  of 
each  wire  round  into  a  ring 
so  as  to  enable  the  wires 
to  stand  upright  and  the 
silk  threads  to  hang  straight 
Suspended  pith  bails.  down.      The    silk    threads 

are  non-conductors,  and  their  use  is  to  insulate  the  pith 
balls.  Rub  the  glass  rod  briskly  with  a  dry  silk  hand- 
kerchief and  bring  its  end  near  one  of  the  pith  balls; 


POSITIVE  AND  NEGATIVE   ELECTRICITY.     295 

the  ball  will  be  attracted  and  fly  towards  it.  If,  how- 
ever, it  touches  the  rod,  it  will  immediately  be  repelled 
and  fly  away  again,  and  cannot  be  induced  to  come 
near  a  second  time.  Rub  the  sealing-wax  sharply  with 
flannel  so  as  to  electrify  it,  and  try  its  effect.  The  ball 
which  was  flying  from  the  glass  is  strongly  attracted  to 
the  wax.  If  we  bring  the  sealing-wax  near  the  other 
ball,  we  shall  find  that  it  will  behave  as  the  first  ball  did 
with  the  glass — first  attracted  by  the  rod  until  it  touches 
it,  and  then  instantly  flying  away  repelled.  If  we  follow 
it  with  the  wax  it  will  keep  edging  away  so  as  to  avoid 
touching  it  again,  but  if  we  offer  it  the  rubbed  glass 
rod  it  will  fly  to  that.  This  experiment  may  be  varied 
by  touching  both  the  pith  balls  with  the  same  rod  ; 
then,  on  bringing  the  balls  near  together,  they  repel  each 
other ;  but  if  one  be  touched  with  the  ^ 

glass  and  the  other  with  the  wax,  they 
will  attract  each  other. 

Taking  off"  the  pith  balls,  attach  a 
wire  loop  to  the  end  of  the  silk  thread 
and  lay  the  excited  wax  in  it.  Then 
rub  a  second  stick  of  sealing-wax  and 
present  its  end  to  the  end  of  the  one 
suspended  in  the  wire,  and  they  will 

Mode  of  suspending 

repel  each  other  vigorously  ;  but  if  the  rod. 

excited  glass  rod  is  held  to  the  suspended  wax  it  will 
be  attracted.  In  the  same  way,  if  we  hung  up  and 
insulated  an  electrified  glass  rod,  it  would  be  repelled  by 
another  excited  glass,  but  attracted  by  excited  wax. 

It  is  plain  from  all  this  that  there  is  something  double 
about  the  electricity.      It  cannot  be  all  just  the  same 


296  THE   FORCES  OF  NATURE. 

thing,  or  why  should  electrified  g'ass  attract  when  elec- 
trified wax  repels  ?  People  talk  about  two  electricities, 
or  two  kinds  of  electricity.  It  is  difficult  to  know  what 
these  words  mean  when  we  do  not  know  the  nature  of 
electric  action ;  but  a  doubleness  of  some  kind  there 
certainly  is,  and  it  is  necessary  to  distinguish  the  two 
things  by  names.  The  electricity  produced  by  rubbing 
glass  with  silk  is  therefore  called  positive  electricity ;  and 
the  other  sort  produced  by  rubbing  sealing-wax  with 
flannel  is  called  negative  electricity.  These  names  do 
not  mean  that  one  has  more  electricity  and  the  other 
less,  but  that  there  is  a  difference  between  them  of  such 
a  nature  that  equal  quantities  of  the  two  opposite 
electricities  when  brought  together  neutralize  each  other, 
and  no  electrification  remains ;  just  as  +  4  and  —  4, 
when  added  together,  make  o. 

We  have  also  learned  from  our  experiments  the  very 
important  fact  that  two  bodies  charged  with  the  same 
kind  of  electricity  repel  one  another,  while  two  charged 
with  different  kinds  attract  one  another. 

By  rubbing  glass  or  sealing-wax  in  the  hand,  as  in 
the  above  experiments,  only  very  small  quantities  of 
electricity  can  be  produced,  but  machines  have  been 
invented  for  rapidly  producing  large  quantities.  Many 
of  them  work  on  the  principle  of  rubbing  glass  or  ebonite 
with  silk,  but  the  glass  is  in  the  form  of  a  cylinder,  or 
of  a  large  circular  plate,  which  is  pressed  hard  against 
a  pad  covered  with  silk,  and  then  turned  quickly  by  a 
handle. 

Electroscopes. — Various  instruments  have  been  made 
by  means  of  which  the  presence  of  electricity,  even  when 


ELECTROSCOPES.  2Q? 

in  very  small  quantities,  may  be  detected  :  such  instru- 
ments are  called  Electroscopes.  The  pith  balls,  or  the 
little  bits  of  paper  in  our  first  experiment,  might,  in  this 
sense,  fairly  be  called  electroscopes,  and  we  may  easily 
find  other  very  simple  ones.  If  we  put  an  egg  in  an  egg- 
cup,  and  balance  on  it  a  wooden  lath  about  three  feet 
long  and  as  thin  as  possible,  then,  on  bringing  near  it  a 
rubbed  glass  rod,  it  will  turn  round  and  try  to  touch  the 
rod.  Or  we  may  try  the  same  experiment  by  balancing 
a  straight  piece  of  straw  on  the  point  of  a  needle.  So 
the  lath  and  the  straw  become  electroscopes. 

The  best  form  for  simple  experimental  purposes  is  that 
known  as  the  gold-leaf  electroscope.  It  consists  of  a  wide- 
mouthed  bottle,  through  the  cork  of  which  is  passed  a  brass 
rod ;  round  the  brass  rod  a  little  shellac  has 
been  melted,  which  prevents  it  touching 
the  cork,  and  so  insulates  the  rod.  The 
top  of  the  rod  ends  in  a  plate  or  knob, 
while  to  the  lower  end,  that  is,  the  end  in- 
side the  bottle,  are  attached  two  pieces  of 
thin  gold-leaf.  When  the  knob  at'  the  end 
of  the  rod  is  touched  with  rubbed  glass, 
electricity  passes  into  the  rod,  and  also,  of 
course,  into  the  gold-leaves,  and  these  being 
charged  with  the  same  kind  of  electricity  TJ  'scope. 
repel  one  another,  and  stand  apart— slightly,  if  the  charge 
is  very  small,  and  more  widely  when  more  electricity  is 
present. 

Let  us  see  what  more  we  can  learn  by  means  of  this 
instrument.  Connect  to  the  rod  of  the  electroscope  a 
long  metallic  wire ;  support  and  insulate  the  other  end  of 


298  THE  FORCES  OF  NATURE. 

the  wire  by  twisting  it  round  a  stick  of  sealing-wax, 
which  may  for  convenience  be  stuck  upright  on  a  bit  of 
wood.  On  touching  the  further  end  of  the  wire  with 
a  rubbed  glass  rod,  the  gold-leaves  will  diverge  as  if  the 
knob  itself  had  been  touched.  Take  off  the  wire,  and 
replace,  it  with  a  piece  of  silk  thread,  and  we  now  find 
that  an  excited  glass  rod  touching  the  thread  has  no 
effect  upon  the  gold-leaves;  they  do  not  move  or  take 
any  notice.  So  we  discover  that  the  silk  is  a  non-con- 
ductor of  electricity,  while  the  wire  is  a  conductor.  But 
we  will  dip  the  silk  in  water,  and  try  the  experiment 
again.  This  time  the  gold-leaves  diverge  as  they  did 
when  the  wire  was  used ;  we  have  turned  the  non-con- 
ducting silk  into  a  conductor  by  wetting  it,  showing  that 
water  is  a  conductor.  Now  you  see  why  we  had  to  be 
so  careful  in  our  earlier  experiments  to  make  everything 
very  dry,  for  where  there  is  any  moisture  it  will  carry 
away  the  electricity  as  fast  as  it  is  produced.  Try  now 
similar  lengths  of  cotton  and  linen  threads ;  you  will  find 
the  linen  a  better  conductor  than  the  cotton,  but  not 
nearly  so  good  as  the  metal  wire.  Linen,  cotton,  and 
string  are  imperfect  conductors  ;  in  fact,  they  do  not  con- 
duct the  ordinary  voltaic  or  current  electricity  which  we 
shall  describe  presently. 

Electric  Distribution. — Warm  the  end  of  a  stick 
of  sealing-wax  in  a  candle,  and  stick  a  penny  on  to  it. 
If  now,  holding  it  by  the  wax-handle,  we  touch  with  the 
penny  any  electrified  body,  part  of  the  electricity  will 
pass  to  the  coin,  and,  being  unable  to  escape  through 
the  non-conducting  wax,  will  remain  upon  it  so  that 
we  can  carry  it  away  to  examine.  .  In  fact,  the  little 


ELECTRIC  DISTRIBUTION.  299 

instrument  acts  like  an  electric  carrier,  with  which  to  carry 
away  a  small  quantity  of  any  charge  ;  its  proper  name  is 
a  carrier  or  proof  plane.  We  can,  of  course,  discharge  it, 
that  is,  cause  the  electricity  to  vanish,  by  letting  it  touch 
a  conductor  joined  to  the  earth ;  the  touch  of  a  finger 
will  do  it. 

Now,  suppose  we  have  a  metallic  ball,  and  wish  to 
test  whether  it  is  charged  with  electricity.  We  lay  the 
carrier  on  it  for  a  moment,  and  then  apply  it  to  the 
knob  of  the  electroscope,  when  the  presence  of  electricity 
will  be  shown  by  the  diverging  of  the  gold-leaves.  But 
supposing  that  instead  of  a  ball  we  have  a  can,  or  hollow 
metal  globe,  charged  with  electricity,  then  the  carrier 
will  show  us  a  new  fact,  i.e.  that  while  we  can  take 
electricity  readily  from  the  outside  of  the  can,  yet,  if  the 
carrier  touches  the  inside,  and  is  then  applied  to  the 
electroscope,  the  gold-leaves  will  not  diverge,  there  is  no 
sign  of  electricity  there.  Whatever  charge  of  electricity 
may  be  given  to  a  vessel,  the  whole  of  it  is  found  on 
the  outside,  and  none  whatever  inside.  This  is  an  im- 
portant fact  to  remember. 

But  though  the  electricity  always  shows  itself  on  the 
outside,  it  is  not  always  distributed  equally  over  the 
surface  of  the  electrified  body.  If,  instead  of  a  round 
ball  of  metal,  we  have  one  in  the  shape  of  an  egg,  and 
electrify  that,  then  by  putting  the  proof  plane  on  different 
parts  of  it  and  touching  the  electroscope,  we  find  that 
the  gold-leaves  move  but  little  with  the  electricity  from 
the  round  end,  but  fly  much  further  apart  when  the 
charge  is  taken  from  the  pointed  end ;  showing  that  most 
of  the  electricity  resides  at  the  point.  In  fact,  if  an 


300 


THE  FORCES   OF  NATURE. 


electrified  body  actually  ends  in  a  sharp  point,  so  much 
of  the  electricity  will  accumulate  on  the  point  that  it 
will  escape  into  the  air,  and  the  body  will  be  discharged^ 
or  emptied  of  electricity. 

Electric  Induction. — You  will  remember  that  when 
we  brought  a  key  near  one  pole  of  a  magnet  (p.  290),  the 
key  became  magnetic,  and  remained  so  as  long  as  the 
magnet  was  near,  but  its  magnetism  disappeared  directly 
the  permanent  magnet  was  taken  away.  A  similar  thing 
occurs  when  we  bring  a  conductor  near  an  electrified 
body ;  the  conductor  becomes  electrified  by  the  presence 


Experiment  illustrating  electric  induction. 

of  the  electric  charge  near  it,  but  loses  its  electrification 
directly  we  remove  the  rubbed  glass  or  other  electrified 
body.  This  influence  exerted  by  an  electric  charge  on 
bodies  in  its  neighbourhood  is  called  electric  induction, 
just  as  the  influence  exerted  by  a  magnet  on  iron  is 
called  magnetic  induction.  And  the  two  are  very  similar ; 
for  the  north  pole  of  a  magnet  by  its  influence  produces 
an  opposite  or  south  pole  in  the  end  of  the  iron  nearest 
to  it,  and  repels  to  the  further  end  of  the  iron  the  similar 
or  north  magnetism ;  so,  also,  a  positively  electrified 
body,  like  rubbed  glass,  attracts  the  opposite  or  negative 


ELECTRIC  INDUCTION.  30! 

electricity  to  the  end  of  any  conductor  near  it,  and  repels 
the  similar  or  positive  electricity  to  the  far  end.  Had 
we  used  a  negatively  electrified  body,  like  rubbed 
sealing-wax,  positive  electrification  would  be  found  on 
the  near  side  of  any  adjacent  conductor,  and  negative 
on  the  distant  side.  In  every  case  this  induced  electrifi- 
cation comes  and  goes  with  the  approach  and  removal 
of  the  charged  body. 

•Many  interesting  experiments  can  be  made  to  illustrate 
electric  induction.  Here  is  one.  Support  a  short  metal 
poker  on  a  dry  and  warm  glass  tumbler  or  other  insu- 
lator, and  connect  one  end  of  it  to  your  electroscope  by 
a  wire  or  damp  thread  (see  p.  300).  Now  bring  rubbed 
sealing-wax,  or  any  electrified  body,  near  to  the  other 
end  of  the  poker ;  notice  how  the  gold-leaves  open  as 
the  electrified  body  comes  near,  and  close  the  moment 
it  is  removed.  The  electric  charge  induced  on  the 
poker  is  shared  by  the  electroscope  which  reveals  its 
presence.  Next  remove  the  connection  with  your  electro- 
scope, and  let  your  electrified  body  remain  near  one 
end  of  the  poker;  now  test,  by  your  little  carrier  and 
electroscope,  the  nature  of  the  electrification  at  each  end 
of  the  poker.  Thus,  if  you  are  skilful,  you  can  easily 
verify  the  statements  in  the  preceding  paragraph. 

There  is  a  remarkable  difference  between  the  condition 
of  the  attracted  and  the  repelled  induced  electric  charge, 
which  can  be  proved  by  the  same  simple  apparatus,  but 
these  and  many  other  interesting  experiments  on  electric 
induction  you  will  learn  if  you  pursue  the  study  of 
Physics,  of  which  electricity  is  one  branch.  The  well- 
known  Leydcn  jai\  which  enables  us  to  accumulate  an 


302  THE  FORCES  OF  NATURE. 

electric  charge,  and  the  Electrophorus,  as  well  as  other 
more  modern  and  powerful  "  influence  machines,"  all 
depend  upon  the  principle  of  electric  induction. 

CURRENT  OR  VOLTAIC  ELECTRICITY. 

As  yet,  in  our  electric  experiments  we  have  been 
chiefly  concerned  with  electricity  remaining  quietly  on 
the  surface  of  a  body  which  has  been  charged  with  it ; 
now  we  must  find  out  something  about  electricity  in 
motion,  and  for  this  we  shall  need  a  little  more  apparatus. 

Go  to  a  tinsmith's  and  get  a  piece  of  sheet  copper  and 
a  piece  of  zinc — a  flat  plate  of  each  about  two  inches 
square,  and  have  a  piece  of  copper  wire  soldered  to 
each.  These  must  be  placed  in  a  jar  or  glass  vessel, 
taking  care  that  the  two  plates  do  not  touch  each  other, 
and  the  jar  must  be  filled  with  dilute  sulphuric  acid,  one 
part  of  the  acid  to  about  twelve  of  water.  If  you  now 
put  the  ends  of  the  two  wires  for  an  instant  on  to  your 
tongue  you  will  find  that  they  produce  a  very  peculiar 
taste  or  feeling. 

Nowr  take  the  compass-needle  (p.  290),  and  wind 
round  it  a  coil  of  several  turns  of  "  covered "  copper 
wire.  Place  the  compass  on  the  table,  and  turn  it  so 
that  the  needle  lies  within  and  parallel  to  the  coil  of  wire. 
If  you  now  touch  the  ends  of  the  wires  from  your  zinc 
and  copper  with  the  two  bared  ends  of  the  wire  of  your 
coil,  you  will  find  the  compass-needle  instantly  driven  on 
one  side.  If  you  change  over  the  wires,  that  is,  put  the 
one  from  the  zinc  where  the  copper  was,  and  vice  versa, 
the  magnetic-needle  will  now  be  driven  to  the  opposite 


CURRENT  OK    VOLTAIC  ELECTRICITY.       303 

side.  Notice  that  you  can  keep  one  wire,  say,  from  the 
/.inc,  twisted  to  the  wire  of  the  coil,  and  no  motion 
of  the  magnetic-needle  is  produced  until  the  other  wire 
(that  from  the  copper)  touches  the  other  end  of  the  coil. 

These  effects  are  owing  to  a  flow  of  electricity  through 
the  wire.  You  will  remember  what  we  learned  (p.  211) 
about  energy  passing  from  one  form  into  another,  and 
about  Chemical  Affinity  as  one  of  the  Forces  (p.  204). 
Now  the  copper  and  zinc  plates  have  a  different  chemical 
affinity  for  the  acid  solution  in  which  they  have  been 
placed  and  which  quickly  begins  to  act  upon  one  of  them, 
and  it  is  found  that  when  the  plates  touch  or  are  connected 
together  by  a  wire,  the  energy  of  the  chemical  action  is 
converted  into  that  of  Electricity,  and  a  eontintious  flow  or 
current  of  electricity  is  kept  passing  through  the  wire 
from  one  plate  to  the  other.  I  said  "  connected  together 
by  a  wire,"  but  it  would  be  more  accurate  to  say  "con- 
nected by  continuous  conductors,"  for  wire  is  only  one 
of  the  conductors  of  electricity,  though  perhaps  the  most 
convenient  for  ordinary  use.  You  may  have  noticed 
already  that  when  you  laid  the  ends  of  the  two  wires 
on  your  tongue  it  was  not  necessary  that  they  should 
touch  each  other  for  you  to  have  the  peculiar  sensation 
given  by  the  current  of  electricity ;  in  this  case,  your 
moist  tongue  is  the  conductor  which  carries  on  the 
current  from  one  wire  to  the  other. 

Such  a  jar  as  we  have  used,  with  its  two  plates  and  its 
liquid,  is  called  a  Voltaic  or  Galvanic  cell,  from  the 
names  of  M.  Volta  and  M.  Galvani,  the  two  famous 
discoverers  of  current  Electricity.  If  we  take  a  number 
of  the  cells  and  connect  them  together  by  short  wires 


304 


THE  FORCES  OF  NATURE. 


passing  from  the  copper  plate  of  each  cell  to  the  zinc  of 
the  next,  we  have  what  is  called  a  voltaic  battery. 

There  are  several  forms  of  voltaic  cells,  usually  called 
after  the  name  of  the  inventor,  and  devised  one  after 
another  in  order  to  get  over  some  difficulty  or  drawback 
in  the  working  of  the  previous  cells.  For  instance,  in 
the  simple  cell  described  above  we  should  find  that  after 
a  time  the  copper  plate  becomes  entirely  covered  with 
bubbles  of  hydrogen  gas,  and  this  quite  prevents  the  cell 
from  giving  any  current.  To  cure  this  defect,  various 
plans  are  adopted.  One  very  good  one,  known  from  its 
inventor  as  Daniell's  battery,  is  making  the  cell  double, 


Simple  form  of  voltaic  battery. 

so  that  the  zinc  should  be  still  in  sulphuric  acid  solution, 
but  the  copper  plate  be  immersed  in  copper  sulphate 
solution.  This  action  of  the  hydrogen  gas  in  adhering 
to  the  copper  plate  and  stopping  the  current  is  called 
Polarization. 

A  current  will  run  through  any  length  of  wire — miles 
of  it — if  the  connection  is  complete ;  but  if  the  bare  wire 
is  anywhere  coiled  in  a  loop,  so  that  one  part  touches 
another,  then  the  current  instead  of  running  all  round 
the  loop  will  take  a  shorter  path  across  the  points 
of  contact,  and  return  without  all  passing  through  the 
whole  length  of  wire.  To  prevent  this,  which  is  called 
short-circuiting  wires  used  for  electrical  purposes  are 
generally  covered  with  cotton  or  silk  or  some  other 


THE  ELECTRIC   TELEGRAPH. 


305 


non-conductor,  so   that   even   if  one   part   of  the  wire 
touches  another  no  short-circuiting  may  take  place. 

If  we  take  a  bar  of  soft  iron,  and  coil  round  it  a  large 
number  of  turns  of  covered  wire,  and  then  connect  the 
ends  of  the  wire  with  an  electric  battery  so  that  a  current 
passes  through  it,  we  shall  find  that  the  iron  has  become 
a  magnet,  and  will  attract  small  pieces  of  iron,  but  the 
moment  that  the  wires  are  disconnected  and  the  current 
ceases  to  flo\v,  the  iron  loses  its  magnetic  power.  Such 


agnetized  by  electric  cur 


an  arrangement  is  called  an  electro-magnet ;  it  is  only 
a  magnet  while  a  current  is  circulating  through  it. 

We  shall  now,  perhaps,  be  able  to  understand  the 
principle  of  the  electric  Telegraph.  Suppose  we  have 
an  electro-magnet — that  is,  the  iron  and  the  coils  round 
it — at  one  place,  and  then  carry  on  the  wires  supported 
by  telegraph  poles  to  a  town  some  miles  distant.  We 
may  call  the  place  where  the  magnet  is  Station  A,  and 
the  place  where  the  ends  of  the  wire  are  Station  B.  At 
Station  A  let  there  be  just  above  the  electro-magnet  a 
small  piece  of  iron  held  by  a  spring,  which  keeps  it 
about  one  quarter  inch  from  the  magnet.  At  Station  B 

x 


3O6  THE  FORCES  OF  NATURE. 

let  there  be  a  battery.  If  at  B  we  connect  the  ends  of 
the  two  wires,  one  to  each  end  of  the  battery,  a  current 
will  flow  along  the  wire  on  the  telegraph-poles  to  the 
magnet  at  A,  and  while  it  is  running  round  the  coils 
the  iron  bar  will  become  a  magnet,  and  attract  down 
the  small  piece  of  iron  suspended  above  it;  but  on 
disconnecting  either  wire  at  B  the  current  stops  passing, 
the  bar  ceases  to  be  a  magnet,  and  the  small  piece  of 
iron  is  drawn  up  again  by  the  spring.  Now,  by  a  system 
of  signals  arranged  beforehand — signals  depending  on 
the  longer  or  shorter  time  during  which  the  iron  is  held 
down  by  the  magnet — an  alphabet  may  be  made,  and, 
therefore,  words  can  be  transmitted.  This  is  the  prin- 
ciple of  one  form  of  telegraph. 

The  earliest  form  of  electric  telegraph,  and  one  still 
used  in  many  places,  is  simply  a  magnetic  needle  sur- 
rounded by  a  coil  of  wire,  like  the  arrangement  described 
on  p.  302,  only  for  convenience  the  needle  and  coil  are 
suspended  vertically.  Instead  of  long  and  short  contacts 
from  the  distant  operator,  a  code  of  signals — for  every 
letter  of  the  alphabet  and  for  the  figures  o  to  9,  etc. — is 
arranged  from  the  right  and  left  movements  of  the 
needle,  which  occur  when  the  current  flows  in  one 
direction  or  the  other. 

From  what  was  said  on  p.  302,  you  will  understand 
how  a  delicately  suspended  magnetic  needle  inside  a 
coil  of  wire  can  be  used  to  detect  the  existence  and  to 
find  the  direction  of  an  electrical  current.  Such  an 
instrument  is  called  a  galvanometer,  and  by  similar  means 
we  can  also  measure  the  strength  of  our  electric  current. 

Another  remarkable  property  of  an  electric  current  si 


ELECTRIC  LIGHT.  307 

its  power  of  chemical  action ;  we  shall  refer  to  this  in  the 
next  chapter.  If  you  dip  the  ends  of  the  wire  from  a 
voltaic  battery  into  a  slightly  acid  water  you  will  see 
bubbles  of  gas  coming  off,  due  to  the  decomposition  of 
the  water.  This  electrical  decomposition  is  called  electro- 
lysis ;  all  liquids  which  are  compounds  (p.  313)  and  which 
transmit  the  current  are  thus  decomposed  into  their  two 
main  constituents,  one  always  going  to  the  place  where 
the  current  enters  the  liquid,  and  the  other  to  the  place 
where  it  leaves  the  liquid.  Fasten  a  silver  coin  to  each 
end  of  the  wires  from  your  battery  and  dip  the  coins, 
about  an  inch  apart,  into  a  solution  of  sulphate  of  copper ; 
you  will  find  the  coin  attached  to  the  zinc  end  of  the 
battery  covered  with  a  deposit  of  copper,  and  if  you 
reverse  the  wires  the  copper  will  now  be  dissolved  off  the 
first  and  appear  on  the  other  coin.  This  is  the  principle 
of  electro-plating,  which  is  so  largely  used  in  the  arts  for 
depositing  silver  or  gold. 

Solids,  owing  to  their  cohesion,  cannot  thus  be  de- 
composed, or  shaken  asunder,  but  the  molecules  of  the 
solid,  if  they  resist  the  passage  of  the  current,  do  get  a 
shaking,  which  takes  the  form  of  heat.  Bad  conductors 
thus  grow  hot  when  an  electric  current  flows  through 
them,  and  if  the  resistance  is  great  enough  and  the 
current  strong  enough  the  conducting  wire  becomes  red- 
hot  and  even  melts.  This  is  the  principle  of  the  electric 
glow-lamps,  now  so  familiar  to  us  all ;  a  thread  of  very 
resisting  material  (a  filament  of  carbon)  enclosed  in  a 
vacuum  being  employed.  Another  and  more  powerful 
method  of  electric  lighting  is  the  arc-light.  Here  the 
current  is  made  to  pass  between  two  carbon  pencils  kept 


308  THE  FORCES  OF  NATURE. 

a  slight  distance  apart,  and  in  jumping  across  the  gap 
great  resistance  is  encountered  and  a  very  brilliant  light 
is  produced.  The  ordinary  voltaic,  or  primary,  batteries 
are  not  used  to  generate  the  current  for  the  electric 
light,  as  they  would  prove  both  expensive  and  trouble- 
some. Special  machines  are  employed,  driven  by 
powerful  steam-engines,  and  the  principle  on  which  they 
work  is  different  from  anything  we  have  learnt  so  far. 

If  we  have  a  coil  of  silk-covered  wire,  with  the  two 
ends  of  the  bare  wire  twisted  together,  and  quickly  thrust 
one  pole  of  a  magnet  into  the  coil,  it  will  be  found  that 
the  magnet  starts  a  momentary  current  in  the  coil,  which 
dies  away  again  immediately.  Pull  the  magnet  pole 
out  and  another  fleeting  current  runs  through  the  wire, 
but  in  the  opposite  direction  to  the  first.  Observe  that 
by  this  we  find  that  just  as  an  iron  bar  is  made  magnetic 
by  being  put  inside  a  coil  through  which  an  electric 
current  is  passing,  so  on  the  other  hand  an  electric 
current  can  be  produced  in  a  coil  by  moving  it  past  the 
ends  of  a  magnet.  So  electric  currents  produce  magnetic 
power,  and  magnetism  in  turn  produces  electric  currents. 

It  is  not  possible  in  this  little  book  for  beginners  to 
explain  the  details  of  the  arrangements  by  which,  with 
the  aid  of  rapidly  revolving  coils  of  wire  and  powerful 
magnets,  machines  are  made  for  producing,  on  this 
principle,  electric  currents  of  enormous  strength.  All 
such  machines  are  called  magneto-electric  machines, 
and  another  type  dynamo-electric  machines;  some  of 
them  are  of  very  great  size,  requiring  engines  of  hundreds 
of  horse-power  to  drive  them. 


(309     ) 


CHAPTER    XXI. 

CHEMISTRY. 

WE  have  already  several  times  mentioned  Chemical 
Affinity  and  Chemical  Action,  and  must  now  turn 
attention  more  closely  to  Chemistry  and  see  what  kind 
of  knowledge  is  classed  under  this  name. 

You  know  that  if  we  allow  milk  to  stand  for  a  long 
time,  especially  if  the  weather  is  hot,  it  will  turn  sour. 
The  milk  will  not  be  the  same  as  it  was  when  first  taken 
from  the  cow ;  in  other  words,  some  change  takes  place 
in  the  milk.  Again,  when  meat  or  eggs,  or  anything 
of  that  kind,  "  goes  bad,"  as  we  say,  what  does  that 
really  mean  ?  It  means  that  these  things  pass  through 
some  alterations  in  which  bad  smelling  substances  take 
the  place  of  good  smelling  substances.  Now,  what 
happens  in  all  these  cases?  What  was  the  original 
substance  of  the  meat,  eggs,  milk,  etc.?  How  came 
they  to  be  changed?  What  are  the  new  and  bad  sub- 
stances? All  these  questions  belong  to  the  study  of 
Chemistry. 

Analysis  of  Water. — In  the  course  of  these  lessons 
we  have  tried  many  experiments  with  our  very  useful 
friend  water.  We  have  seen  it  frozen  into  ice,  boiled 
into  vapour,  and  brought  back  from  both  these  conditions 


310  THE  FORCES  OF  NATURE. 

to  water  again ;  we  have  dissolved  things  in  it,  and 
weighed  it,  and  pumped  it,  and  made  it  work  for  us. 
Now,  let  us  take  it  once  more,  and  try  to  find  out  what 
it  is  made  of.  For  this  purpose  we  will  send  through 
it  a  current  of  electricity. 

Take  a  glass  vessel  with  a  hole  in  the  bottom  of  it — a 
lamp-shade   of  this  shape  turned  upside  down  will  do 


Decomposition  of  water  by  electric  current. 

admirably;  stop  up  the  smaller  opening  with  a  large 
cork,  through  which  two  wires  have  been  passed,  and 
pour  water  into  the  vessel,  adding  also  a  few  drops  of  an 
acid  to  make  the  water  a  better  conductor.*  The  outer 

*  The  common  but  poisonous  and  corrosive  acid  called  oil  of 
vitriol — the  chemical  name  for  which  is  sulphuric  acid — is  best 
to  use ;  but  here,  as  in  many  other  chemical  experiments,  great 
care  must  be  taken  not  to  spill  any  acid  on  your  fingers  or  clothes, 
or  a  very  bad  burn  will  follow.  The  wires  in  the  vessel  should  be 
of  the  metal  platinum,  for  a  reason  that  will  be  explained  presently. 
The  cork  can,  if  necessary,  be  made  water-tight  by  melting  a  little 
paraffin  wax  from  a  candle  over  it. 


DECOMPOSITION  OF  WATER  BY  ELECTRICITY.  311 

ends  of  the  wire  must  now  be  connected  with  the  wires 
of  a  voltaic  battery  (which  must  have  at  least  two  cells ; 
these  we  have  already  described  in  the  chapter  on 
Electricity),  and  then  an  electric  current  will  begin  to 
flow  round  through  the  battery  and  the  wires  and  the 
water.  The  moment  it  does  so  you  will  see,  rising  through 
the  water  from  the  surface  and  points  of  the  wires,  little 
bubbles  of  gas,  which  can  be  collected  in  the  following 
way.  Take  a  clean  empty  bottle  (a  narrow  one  with 
a  small  mouth  will  do  best),  fill  it  quite  to  the  brim  with 
water,  and  then,  putting  your  thumb  over  the  open  top, 
turn  it  upside  down  with  its  mouth  under  the  water  in  the 
basin,  and  bring  it  over  one  of  the  wire  points.  Another 
bottle  must  be  filled  and  inverted  in  the  same  manner 
over  the  other  wire,  so  that  the  gas-bubbles  will  rise 
into  the  bottles,  turning  out  the  water  in  them  and  taking 
its  place.  If  the  two  bottles  are  placed  over  the  wires 
at  the  same  instant,  we  shall  presently  find  that  when 
one  bottle  is  just  filled  up  with  gas  the  other  is  only 
half  full.  Now,  where  do  these  gases  come  from,  and 
what  are  they  ?  They  come  out  of  the  water,  which  has 
been  broken  up  by  the  electric  current,  and  they  are  the 
actual  substances  of  which  the  water  was  formed.  If 
we  were  to  mix  these  two  gases  together  again  and  then 
bring  a  lighted  match  to  them,  they  would  "go  off" 
with  a  big  bang  and  a  tiny  drop  of  water  would  again 
be  formed,  the  drop  which  was  broken  up,  or,  as  we 
say,  decomposed  by  the  electricity.  From  this  experiment, 
then,  we  learn  the  very  important  fact  that  water  is  made 
up  of  two  gases,  and  that  we  can  either  obtain  the  gases 
from  the  water,  or  the  water  from  the  gases. 


312  THE  FORCES  OF  NATURE. 

Now  let  us  turn  our  attention  to  these  two  gases  them- 
selves. We  will  try  some  experiments  on  them  and  find 
out  something  about  them. 

Take  the  bottle  which  first  filled  with  gas.  Lift  it 
out  of  the  water,  carefully  keeping  it  still  upside  down, 
and  wipe  it  lightly  outside.  Put  a  lighted  match  to  its 
mouth,  and  notice  that  the  gas  will  take  fire  and  burn  like 
the  coal  gas  we  use  in  our  lamps,  but  the  flame  is  very 
pale  and  blue.  Now  plunge  the  lighted  match  right  into 
the  bottle ;  it  immediately  goes  out.  This  gas,  then,  will 
burn  if  set  fire  to,  but  it  will  not  let  a  match  burn  in 
it.  It  is,  as  you  can  see,  quite  colourless  and  invisible, 
and  it  is  also  quite  without  taste  or  smell.  The  name 
given  to  it  is  Hydrogen.  This  is  not  the  first  time  we 
have  heard  of  Hydrogen  ;  in  the  chapter  on  Weight  and 
Pressure  (p.  226),  it  was  spoken  of  as  lighter  than  air. 
It  is  the  lightest  of  all  substances,  its  weight  being  less 
than  one-fourteenth  the  weight  of  air,  so  that  it  is  used 
to  fill  balloons  which  will  rise  and  float  in  the  air.  In 
fact,  it  is  so  light  that  if  you  want  to  keep  it  in  a  jar 
even  for  a  few  minutes,  the  jar  must  be  turned  upside 
down  to  prevent  it  from  all  flying  away  upwards. 

No\v  consider  the  gas  in  the  other  bottle,  which  is  also 
colourless,  invisible,  and  tasteless.  Try  and  light  it ;  it 
will  not  take  fire.  Blow  out  the  lighted  match,  or  set  fire 
to  the  end  of  a  bit  of  string  and  blow  it  out,  in  either 
case  so  as  to  leave  a  red-hot  tip ;  plunge  this  into  the 
gas,  and  the  spark  will  burst  out  again  into  flame.  The 
properties  of  this  gas,  then,  are  different  from  those  of 
hydrogen,  for  it  will  not  itself  burn,  but  encourages  other 
things  to  burn  in  it.  It  is  also  an  old  acquaintance ;  we 


ELEMENTS  AND   COMPOUNDS.  313 

have  met  with  it  several  times  under  the  name  of  Oxygen. 
We  found  that  when  carbon  is  burning  it  is  combining 
with  oxygen,  that  animals  in  breathing  draw  oxygen 
into  their  lungs  to  purify  the  blood  (p.  152),  and  that 
plants  in  light  are  constantly  giving  it  off  (p.  195). 

We  have  now  split  up  water  into  the  two  gases  of 
which  it  is  formed,  and  we  find  on  examination  that 
these  two  gases  are  Hydrogen  and  Oxygen.  This 
process  of  splitting  up  a  substance  so  as  to  divide  it 
into  all  the  different  kinds  of  matter  of  which  it  is 
made  is  called  analyzing  the  substance.  We  have 
analyzed  the  water.  The  usual  mode  of  analysis  is  by 
chemical  means,  an  example  of  which  is  given  on  p.  318. 

Elements  — Some  substances  have  never  been  divided 
or  analyzed  at  all.  Take,  for  instance,  gold,  silver, 
oxygen,  or  hydrogen ; — do  what  we  will  to  them,  no  one 
has  ever  got  anything  out  of  them  which  is  not  gold, 
silver,  oxygen,  or  hydrogen.  These  are  called  simple 
substances,  or  Elements,  while  those  from  which  it  is 
possible  to  get  more  than  one  kind  of  matter,  such  as 
water,  marble,  etc.,  are  called  Compounds. 

We  should  hardly  have  guessed,  by  looking  at  it,  that 
water  was  not  a  simple  substance ;  but  there  can  be  no 
doubt  of  the  fact  when  we  have  divided  it  into  oxygen 
and  hydrogen,  and  reproduced  it  by  putting  these 
together  again. 

Now,  what  other  Elements  are  there  found  in  the 
world?  Chemists  have  been  at  work  for  many  years 
examining  and  testing  and  analyzing  substances,  and 
when  they  find  one  that  they  cannot  by  any  art  divide 
further,  they  suppose  that  it  is  simple,  and  call  it  an 


314  THE  FORCES  OF  NATURE. 

element;  but,  of  course,  more  knowledge  might  some 
day  show  that  they  were  mistaken  about  some  of  them. 
At  present  there  are  believed  to  be  between  seventy 
and  eighty  Elements  or  simple  substances.  Some  of 
these  have  been  discovered  quite  recently ;  in  fact, 
during  the  printing  of  this  book,  the  very  air  we  breathe 
has  been  found  to  contain,  besides  its  well-known  gases, 
which  form  the  bulk  of  the  atmosphere,  some  new  elements 
which  have  never  been  detected  before.  The  number 
of  Compounds  is  enormously  large,  quite  past  counting. 

Combination :  Mixture. — A  chemical  Compound, 
however,  does  not  mean  simply  a  mixture  of  two  sub- 
stances together,  as  we  might  mix  sugar  with  salt.  In 
such  a  mixture  the  particles  of  sugar  and  salt  lie  side 
by  side  unchanged,  and  if  you  taste  it  you  can  distinguish 
both  the  sugar  and  the  salt  at  the  same  time.  But  when 
two  substances  are  united,  or  chemically  combined,  as 
the  proper  phrase  is,  into  a  compound,  they  always 
produce  something  entirely  different  and  with  different 
properties  from  either  of  them  singly.  For  instance,  we 
have  just  found  that  hydrogen  will  readily  burn,  and 
oxygen  readily  allows  things  to  burn  in  it;  but  when 
they  are  chemically  combined  they  form  water,  which 
will  neither  burn  nor  allow  anything  to  burn  in  it — 
indeed  it  extinguishes  fire. 

Take  some  very  fine  copper  filings  and  mix  them  with 
some  powdered  sulphur.  You  can  distinguish,  at  least 
with  a  microscope,  the  little  particles  of  yellow  sulphur 
and  of  red  copper  lying  side  by  side ;  and  if  some  of  the 
mixture  is  thrown  into  a  basin  of  water  the  sulphur  will 
rise  to  the  top,  while  the  copper  will  sink  to  the  bottom. 


COMBINATION  AND  MIXTURE. 


315 


Now  put  some  of  the  mixture  into  a  small  glass  test-tube 

and  heat  it  over  a  spirit-lamp ;  the  sulphur  will  soon  melt, 

the  whole  will  get  very  red  hot,  and  then  quite  a  new 

substance    will    have    been 

formed.       Examine    it;     it 

does    not    look    like   either 

copper     or     sulphur ;     you 

cannot   see   small    particles 

of  either,  but  only  a  black 

mass,  and   if  you  throw   it 

into    water    it    sinks    as    a 

whole.       This     experiment 

shows     the    difference    be- 


Sulphur  and  copper  heated  in  a 
test-tube. 

tween  a  chemical  compound  and  a  mixture.  As  long  as 
the  properties  of  the  substances  remain  unchanged  it 
remains  a  mere  mixture;  when  a  new  substance  with 
different  properties  is  produced  by  their  union,  we  know 
that  chemical  combination  has  taken  place. 

Several  pretty  experiments  may  be  made  to  illustrate 
this  point.  Take  some  of  a  very  strong  solution  of 
calcium  chloride,  and  add  to  it  very  carefully  some 
moderately  strong  sulphuric  acid ;  both  of  these  are 
colourless  liquids,  but,  when  put  together,  a  white 
solid  substance  will  be  formed.  The  vessel  into  which 
they  were  poured  may  even  be  turned  upside  down, 
but  nothing,  or  at  most,  a  few  drops  of  water,  will  run 
out.  Here,  then,  is  a  solid  produced  from  two  liquids. 

Again,  get  from  the  chemist  some  sal  ammoniac,  a 
white,  crystalline,  somewhat  fibrous  substance;  powder 
some  of  it  and  mix  it  with  some  ordinary  lime.  Notice 
that  neither  of  the  substances  has  any  appreciable 


3l6  THE  FORCES  OF  NATURE. 

smell.  But,  after  mixing,  and  gently  warming  the  mixture, 
smell  it  again — very  cautiously,  mind — and  you  will  find 
that,  owing  to  some  portion  of  these  two  solids  having 
chemically  acted  upon  each  other,  a  very  strong  smelling 
gas,  ammonia,  which  is  present  in  all  smelling  salts,  has 
been  set  free. 

So  chemical  changes  may  turn  solids  into  liquids  or 
gases,  liquids  into  solids  or  gases,  and  also  gases  into 
solids  or  liquids. 

Table  of  Elements.— The  following  table  contains 
some  of  the  most  important  among  the  substances  re- 
cognized as  Elements.  You  will  see  that  they  are 
arranged  for  convenience  into  two  classes,  metals  and 
non-metals  : — 

Metals. 

Iron.  Aluminium. 

Lead.  Calcium. 

Copper.  Magnesium. 

Zinc.  Sodium. 

Tin.  Potassium. 

Gold.  Lithium. 

Silver. 

Platinum. 

Mercury. 

Non-Metals. 

Oxygen.  Silicon. 

Hydrogen.  Phosphorus. 

Nitrogen.  Sulphur. 

Chlorine.  Bromine. 

Carbon.  Iodine. 

Metals. — Of  these  Metals  those  in  the  first  column 
have  long  been  known,  and  are  among  the  most  useful 
to  man  in  the  various  arts  and  manufactures.  The 
metals  in  the  second  column  have  all  been  discovered 


METALS  AND   NON-METALS.  317 

during  the  present  century;  they  have  many  properties 
in  common,  they  are  never  found  pure  or  "native"  in 
the  earth,  as  they  combine  so  easily  with  oxygen,  and 
all  of  them  when  combined  with  oxygen,  silicon,  etc., 
form  an  important  part  of  the  solid  rocks  and  soils  of 
the  earth,  Aluminium  being  the  principal  ingredient  in 
clay,  Calcium  in  chalk,  etc.  Sand  and  quartz,  however, 
contain  only  the  non-metal  Silicon  combined  with  oxygen. 
The  Metals,  as  a  rule,  are  heavy,  that  is,  heavier  than 
water,  and  will  therefore  sink  to  the  bottom  if  put  into 
a  basin  of  water;  but  Lithium,  Sodium,  and  Potassium 
are  very  light,  and  will  float  on  the  surface.  Moreover, 
they  decompose  water,  dividing  it  into  oxygen  and 
hydrogen  as  the  electric  current  did ;  and  when  water 
is  decomposed  in  this  manner  the  hydrogen  which 
comes  off  usually  takes  fire,  while  the  oxygen  combines 
with  the  metal,  and  forms  a  compound  which  will  dis- 
solve in  the  water  and  make  it  feel  soft  and  soapy. 
These  three  curious  metals  are  so  soft  that  they  are 
easily  cut  with  a  knife,  and  Lithium  may  even  be  spread 
like  butter. 

Lithium  is  the  lightest  solid  known.  The  heaviest  of 
the  well-known  metals  is  Platinum,  which  is  more  than  2  r 
times  as  heavy  as  water.  Gold  is  19  times,  Mercury,  or 
quicksilver,  13^-,  Lead  n,  Silver  10,  Copper  8,  Iron  7$ 
times  as  heavy  as  water,  while  Lithium  is  only  half  the 
weight  of  water. 

Non-metals.. — Of  the  above  non-metallic  Elements 
four  are  gases — oxygen,  hydrogen,  nitrogen,  and  chlorine. 
Of  the  first  two  we  have  already  learnt  something.  The 
last,  chlorine,  is  a  yellowish-green  gas,  has  a  very  bad 


3l8  THE  FORCES   OF  NATURE. 

smell,  and  will  kill  any  one  who  breathes  it ;  even  a  little 
of  it  produces  violent  coughing.  We  will  leave  it  alone 
at  this  early  stage  of  chemical  study ;  but  nitrogen  is 
very  important  to  us,  and  must  be  examined  more 
closely.  In  fact,  the  atmosphere,  the  air  we  breathe, 
is  made  up  of  oxygen  and  nitrogen ;  both  gases  re- 
taining their  own  properties,  so  that  it  is  not  a  chemical 
combination,  but  a  mixture. 

We  can  prepare  nitrogen  by  taking  away  the  oxygen 
from  the  air;  and  a  very  simple  means  of  doing  this, 
and  one  you  can  try  for  yourself,  is  as  follows."""  Get 
some  clean  iron  filings  or  turnings  and  tie  them  up  in 
a  little  muslin  bag ;  by  means  of  a  stiff  piece  of  wire  or 
a  stick  support  the  bag  of  filings  at  the  top  of  a  tall 
glass  jar,  standing  upside  down  in  a  basin  of  water,  as 
shown  in  the  picture.  The  jar  is  of  course  full  of  air, 
though  called  "  empty."  If  you  have  not  got  a  glass 
jar,  a  large  wide-mouthed  bottle  will  do,  or  a  lamp 
chimney  tightly  corked  at  one  end.  Just  before  making 
the  experiment,  moisten  well  the  little  bag  of  filings  (it 
is  best  to  dip  them  into  a  solution  of  sal-ammoniac), 
now  put  the  jar  or  bottle  over  them,  and  leave  the  whole 
standing  in  the  position  shown  in  the  picture  till  the 
following  day.  When  some  24  hours  have  elapsed  you 

*  The  usual  and  the  quickest  way  of  preparing  Nitrogen  is  to 
burn  a  piece  of  phosphorus  inside  a  jar  of  air.  The  phosphorus 
combines  with  the  oxygen,  forming  white  fumes  of  an  oxide  of 
phosphorus  which  rapidly  dissolve  in  water.  If  you  try  this  ex- 
periment, get  your  teacher's  help,  for  phosphorus  is  a  dangerous 
substance  for  you  to  handle,  and  requires  to  be  kept  and  cut  under 
water,  and  not  touched  with  the  ringers,  as  it  catches  fire  so  very 
easily  and  produces  a  horrible  burn.  The  experiment  with  the  iron 
filings  is  quite  easy  and  harmless. 


NITROGEX. 


319 


will  notice  the  water  has  risen  in  the  jar ;  in  a  cylindrical 
jar  10  inches  high  you  will  find  just  2  inches  of  water 
have  entered  the  jar.  What  is  the  reason  for  this  ?  The 
explanation  is  that  the  iron  filings,  or  some  part  of  them, 
have  combined  with  the  oxygen  of  the  air  inside  the 
jar,  and  are  thereby  changed  into  an  oxide  of  iron,  a 
black  rust,  and  the  gas  now  left  in  the  jar  is  no  longer 
air,  but  Nitrogen.  The  water  has  risen  to  take  the  place 
of  the  oxygen  which  has  disappeared,  and  as  the  water 


"61 


Preparation  of  nitrogen  from  atmospheric  air. 

now  occupies  one-fifth  of  the  whole  volume  of  the  jar, 
this  shows  the  important  fact  that  only  one-fifth  of  the 
air  consisted  of  oxygen.  The  remaining  four-fifths  is 
Nitrogen. 

Now  slip  a  card,  large  enough  to  cover  the  mouth  of 
the  jar,  beneath  the  water;  holding  the  jar  with  one- 
hand,  and  pressing  the  card  against  the  mouth  of  the 
jar  with  the  other,  deftly  turn  the  jar  upside  down,  and 
let  it  stand  on  the  table.  Light  a  match  or  paper  spill, 


320  THE  FORCES  OF  NATURE. 

and,  removing  the  card,  dip  the  light  into  the  jar;  it 
instantly  goes  out.  The  gas  neither  takes  fire  nor  allows 
the  match  to  burn  in  it.  Make  this  experiment,  and 
repeat  it,  in  a  quiet  deliberate  manner.  Now  see  if  you 
can  taste  or  smell  the  gas.  Breathe  a  mouthful ;  it  has 
no  taste  nor  smell,  and  certainly  it  has  no  colour ;  like 
the  air,  it  is  quite  invisible.  Nitrogen  gas  seems,  indeed, 
to  be  characterized  by  the  number  of  things  it  cannot 
do,  and  to  be  so  uninteresting  a  substance  that  it  is 
rather  surprising  to  find  that  it  forms  so  large  a  pro- 
portion of  all  the  air.  Its  great  use  in  the  air  seems 
to  be  to  dilute  the  oxygen,  and  prevent  it  from  com- 
bining with  substances  as  rapidly  and  violently  as  it 
would  do  if  there  were  not  something  to  moderate  its 
action. 

But  although  Nitrogen  itself  is  not  very  interesting, 
the  case  is  quite  different  with  its  compounds,  which 
have  very  conspicuous  properties.  Many,  for  instance, 
of  the  most  brilliantly  coloured  dyes  are  compounds 
containing  nitrogen ;  so  are  gunpowder,  dynamite,  nitro- 
glycerine, and  other  explosives;  and  among  yet  other 
nitrogen  compounds  are  some  of  the  most  violent  poisons 
known,  such  as  morphia,  strychnine,  and  prussic  acid. 
The  strong-smelling  ammonia  gas  is  made  of  nitrogen 
and  hydrogen;  it  very  easily  dissolves  in  water,  and  a 
solution  thus  formed  is  the  ordinary  liquid  ammonia  of 
the  chemist's  shop.  Nitric  acid,  a  compound  of  nitrogen, 
hydrogen,  and  oxygen,  is  one  of  the  strongest  acids 
known,  very  poisonous,  and  violently  corrosive.  If 
dropped  on  to  copper,  silver,  or  zinc,  it  eats  into  them 
very  quickly ;  and  if  it  gets  on  to  the  skin  it  burns 


CARBON.  321 

that  too,  and  may  leave  a  bad  sore,  so  that  it  must  be 
handled  with  the  greatest  care. 

^Besides  the  four  gases,  the  only  other  non-metallic 
Elements  are  Carbon,  Bromine,  Iodine,  Fluorine, 
Sulphur,  Phosphorus,  Silicon,  Boron,  Selenium,  and 
Tellurium,  so  that  they  are  but  few  in  comparison  with 
the  metals. 

Carbon  is  a  solid  substance,  which  forms,  when  com- 
bined with  oxygen  and  hydrogen,  almost  all  vegetable 
matter ;  plants  contain  also  combined  nitrogen,  and  the 
flesh  of  animals  consists  of  the  same  four  elements. 
Coal,  which  is  the  remains  of  old  plants  pressed  together 
and  buried  in  the  earth,  is  therefore  very  rich  in  carbon, 
and  coke  or  charcoal  is  almost  pure  carbon.  So  is  the 
mineral  named  graphite,  or  the  so-called  black  lead  in 
our  pencils — which  really  has  nothing  to  do  with  lead ; 
and  another  form  of  pure  carbon  is  the  diamond,  the 
most  beautiful  and  precious  of  jewels. 

The  carbon  compounds  burn  readily,  and  we  use  them 
to  procure  heat  and  light.  Coals  and  coal-gas,  wood, 
paper,  alcohol,  or  spirits — which  are  all  vegetable  pro- 
ducts—tallow, and  other  animal  and  vegetable  fatty  and 
oily  substances,  and  also  the  so-called  mineral  oils, 
paraffin,  naphtha,  etc.,  are  all  com^unds  of  carbon. 

It  is  a  curious  thing  that  the  same  pure  Element 
should  be  able  to  exist  in  various  forms,  and  the  account 
of  how  it  happens  belongs  to  more  advanced  chemistry ; 
but  carbon  is  not  the  only  element  which  behaves 
thus,  sulphur  and  phosphorus  and  some  other  things 
being  also  found  pure  in  different  conditions.  The 
name  given  to  this  peculiarity  is  Allotropy :  charcoal, 


322  THE  FORCES  OF  NATURE. 

graphite,  and  diamond,  are  called  allotropic  forms  of 
carbon. 

Ordinary  Phosphorus  is  a  yellow  waxy  substance, 
poisonous,  and,  as  we  have  seen,  so  inflammable  that 
it  must  always  be  kept  under  water.  The  other,  or 
allotropic  form  of  phosphorus,  is  a  dark  red  powder,  not 
at  all  so  inflammable,  nor  so  poisonous — very  different, 
therefore,  from  the  first  variety.  The  tips  of  ordinary 
matches  are  covered  with  a  phosphorus  mixture,  which 
easily  ignites  by  the  heat  produced  in  striking  the 
match :  with  safety  matches,  however,  which  strike  only 
on  the  box,  no  phosphorus  is  placed  on  the  match 
head,  but  the  brown  preparation  on  the  box  chiefly 
consists  of  the  red  phosphorus. ::" 

Phosphorus  is  obtained  from  bones,  the  earthy  part 
of  which  is  a  compound  of  phosphorus,  oxygen,  and 
calcium,  called  phosphate  of  calcium. 

Most  of  us  are  familiar  with  the  ordinary  form  of 
Sulphur,  or  Brimstone,  a  yellow,  solid,  light  substance. 
If  a  little  is  placed  in  a  test-tube  and  heated  gently,  it 
will  first  melt  and  form  an  amber-yellow  liquid;  when 
further  heated  the  liquid  becomes  darker  in  colour  and 
thicker,  so  thick,  indeed,  that  the  tube  may  be  turned 
upside  down  and  nothing  will  run  out.  On  still  further 
heating,  it  gets  almost  black  and  thinner,  and  finally  it 
boils.  If,  just  as  it  begins  to  boil,  it  is  poured  out  in 
a  thin  stream  into  some  cold  water,  it  will  instantly 

*  A  terrible  disease  of  the  jaws  is  liable  to  be  produced  in  the 
men  and  women  who  are  engaged  in  making  the  poisonous  com- 
mon match,  so  that  in  several  civilized  countries,  but,  alas  !  not  in 
England,  their  manufacture  is  prohibited.  The  safety  matches  are 
harmless  to  the  maker. 


OXIDATION.  323 

become  solid,  but  will  form  a  yellow  stringy  mass  just 
like  india-rubber.  This  is  called  plastic  sulphur,  and  is 
an  allotropic  form  of  sulphur. 

Bromine  is  a  dark  red  liquid,  with  a  very  bad  smell, 
the  only  element  except  Mercury  or  Quicksilver  which 
is  liquid  at  ordinary  temperatures ;  and  Iodine  is  a  bluish 
black  solid,  smelling  something  like  Bromine,  only  not 
so  bad.  The  elements,  Chlorine,  Bromine,  and  Iodine, 
are  very  like  one  another  in  their  properties. 

We  have  spoken  of  only  a  few  out  of  the  long  list  of 
elements,  some  of  which  are  very  rare,  and  many  others, 
though  not  without  importance,  are  not  found  in  very 
large  quantities,  so  that,  in  fact,  the  greater  part  of  the 
earth  and  the  things  upon  it  (including  the  water  and 
the  air)  are  principally  composed  of  some  ten  or  twelve 
elements,  combined  together  in  many  different  forms 
and  proportions. 

Of  these  Oxygen  is  by  far  the  most  important."  Mixed 
with  nitrogen,  it  forms  the  air ;  combined  with  hydrogen, 
it  produces  all  the  water  in  the  world ;  it  is  an  essential 
part  of  all  vegetable  and  of  all  animal  matter,  and  in 
its  various  combinations  it  forms  fully  half  the  material 
of  the  solid  crust  of  the  earth. 

Oxidation. — Oxygen  can  combine  with  almost  all  the 
elements,  and  a  special  name  is  given  to  the  substances 
composed  of  an  element  combined  only  with  oxygen ; 
they  are  called  oxides. 

When  a  piece  of  bright  iron  is  left  out  in  the  air,  it 
will  soon  rust,  as  we  say,  especially  if  the  weather  is 
damp,  and  the  rust  is  merely  a  compound  of  the  iron 
with  some  of  the  oxygen  in  the  air;  there  is  a  black 


324  THE  FORCES  OF  NATURE. 

and  a  red  oxide  of  iron  ;  the  latter,  the  red  rust,  is  called 
in  Chemistry  Ferric  Oxide. 

Get  some  magnesium  ribbon  at  the  chemist's  shop, 
cut  off  a  piece  about  six  inches  long,  hold  it  by  a  pair 
of  pincers  over  a  plate,  and  set  fire  to  it ;  it  will  burn 
with  a  very  brilliant  white  light,  and  when  it  is  burnt 
out,  instead  of  the  bright  shining  metal  we  shall  find 
on  the  plate  only  some  white  powder.  This  is  a  com- 
pound of  oxygen  and  magnesium  called  Oxide  of 
Magnesium,  or  Magnesia. 

If  we  put  a  small  piece  of  the  soft  metal,  Sodium, 
into  a  spoon  and  hold  it  over  a  flame,  it  will  melt,  take 
fire,  and  burn  with  a  yellow  light,  and  a  white  powder 
will  be  formed  which  is  Oxide  of  Sodium,  or  Soda.  We 
may  notice  that  when  the  piece  of  sodium  was  cut  off 
for  this  experiment  there  was  barely  time  to  see  the 
bright  newly-cut  surface  of  the  metal  before  a  thin  layer 
of  the  oxide  began  to  form  over  it,  and  make  it  dull. 
This  is  what  is  meant  by  saying  that  a  metal  tarnishes. 
Silver  does  not  tarnish  easily,  that  is,  it  does  not  readily 
form  oxides  by  simple  exposure  to  the  air;  gold  and 
platinum  do  not  tarnish,  or  oxidize,  at  all  in  this  way, 
only  with  difficulty  can  they  be  made  to  unite  with 
oxygen.  Hence  their  great  value  for  many  chemical  as 
well  as  ornamental  purposes  ;  and  so  we  see  that  elements 
differ  from  each  other  in  the  ease  and  rapidity  with 
which  they  combine  with  oxygen.* 

*  If  iron  wires  had  been  used  in  the  experiment  of  decomposing 
water  by  an  electric  current  (p.  310)  the  oxygen  set  free  would 
immediately  have  combined  with  the  iron  ;  hence  it  is  necessary  to 
use  platinum  wires,  because  platinum  does  not  combine  directly 
with  oxygen. 


ACIDS.  325 

The  examples  just  given  are  all  of  them  oxides  of 
metals,  but  oxygen  combines  also  with  the  non-metals, 
and  the  oxides  so  formed  are  very  interesting  in  their 
properties. 

We  saw  one  of  them  in  the  experiment  with  burning 
phosphorus  :  the  white  fumes  with  which  the  glass  was 
filled  by  the  burning  consisted,  as  we  said  (see  foot- 
note on  p.  318),  of  an  oxide  of  phosphorus.  In  our 
experiment  this  was  all  presently  dissolved  in  the  water, 
but  if  the  oxide  is  wanted  for  separate  examination  the 
experiment  may  be  repeated  on  a  dry  plate,  when 
the  flames  will  settle  as  a  coating  over  the  inside  of  the 
glass.  After  the  phosphorus  has  burnt  out,  the  glass 
can  be  lifted  up,  and  the  white  powder  scraped  off  into 
a  little  heap  on  the  plate.  A  drop  of  water  let  fall  into 
this  heap  combines  so  rapidly  with  the  oxide  that  it  will 
hiss  as  it  would  when  falling  on  red  hot  iron. 

Hence,  after  burning  phosphorus  over  water,  the  white 
fumes  that  dissolved  in  the  water  and  disappeared, 
formed  a  fresh  compound  made  of  oxide  of  phosphorus 
and  water,  which  is  called  Phosphoric  Acid. 

Acids. — Acids  have  a  peculiar  sharp,  sour  taste,  whicli 
we  can  only  describe  as  an  acid  taste,  but  with  which 
we  are  all  very  familiar  in  such  compounds  as  lemon 
juice,  vinegar,  unripe  apples,  etc.  It  would  not  be  safe 
to  try  all  acids  by  tasting  them,  but  a  good  test  is  found 
in  a  substance  called  Litmus,  which  changes  colour  when 
touched  by  an  acid,  so  that  a  purple  or  blue  solution 
of  litmus,  or  a  piece  of  paper  coloured  blue  by  litmus, 
will  turn  red  if  any  acid  is  poured  on  it.  If  pieces  of 
zinc  or  iron  are  put  into  an  acid  solution,  hydrogen  gas 


326  THE  FORCES  OF  NATURE. 

is  always  given  off,  the  result  of  decomposition  of  the  water. 
This  action,  however,  though  characteristic  of  acids,  is  not 
equally  strong  in  all,  and  phosphoric  acid  does  not  show 
it  at  all  so  well  as  sulphuric.  In  fact,  the  best  method 
of  obtaining  hydrogen  for  experiments  is  not  by  pass- 
ing an  electric  current  through  water,  but  by  pouring 
sulphuric  acid  largely  diluted  with  water  on  small  pieces 
of  zinc,  when  bubbles  of  hydrogen  begin  rapidly  to  rise 
through  the  water  :  the  zinc  robs  the  water  of  its  oxygen, 
uniting  with  it,  and  then  with  the  sulphuric  acid,  forming 
a  substance  called  sulphate  of  zinc,  which  is  quickly 
dissolved  by  the  water. 

Now,  notice  this.  Oxide  of  phosphorus  combined  with 
water  produces  Phosphoric  add ;  oxide  of  sulphur  with 
water  produces  a  strong,  burning  acid,  called  Sulphuric ; 
oxide  of  nitrogen  with  water  produces  Nitric  acid.  But 
phosphorus,  sulphur,  and  nitrogen  are  non-metallic 
elements,  and  so  we  find  that  the  oxides  of  non-metals 
with  water  produce  the  compounds  called  acids. 

Alkalies. — Compare  the  oxides  of  the  metals  with 
these  acids.  Take  some  of  the  white  powdered  Soda,  or 
oxide  of  sodium,  \vhich  was  produced  by  burning  sodium, 
and  put  it  into  a  vessel  of  water ;  it  dissolves  easily  in 
the  water,  though  not  quite  as  quickly  as  the  oxide  of 
phosphorus  did,  and  forms  a  solution  of  soda.  Taste 
this  solution  :  it  has  a  queer  taste  of  its  own,  rather 
soapy,  but  certainly  not  acid.  Try  its  effect  on  litmus ; 
it  turns  the  red  litmus  blue,  seeming  to  have  just 
opposite  properties  from  those  of  acids.  It  belongs  to 
a  class  of  substances  we  call  alkalies. 

Now   mix  it   with   an    acid    solution.     To   a    strong 


ALKALIES— SALTS— BASES.  327 

solution  of  soda  add  very  carefully  some  strong  nitric 
acid ;  you  will  notice  that  when  these  two  cold  liquids 
are  put  together  they  become  quite  hot.  Heat  is  always 
given  out  when  substances  combine  chemically.  If  we 
test  the  combination  with  litmus  we  find  that  there  is 
no  change  of  colour,  provided  we  have  put  exactly  the 
right  quantity  of  acid — this  the  litmus  paper  tells  us ;  the 
acid  will  not  turn  it  red,  and  the  alkali  will  not  turn  it 
blue ;  they  have  combined  and  neutralized  each  other's 
effects. 

But  as  the  solution  gradually  cools  some  fine  white 
crystals  will  be  formed  in  it.  We  want  to  observe  these 
particularly,  so  we  will  carefully  pour  off  the  liquid  and 
examine  them.  The  substance  does  not  taste  at  all  like 
the  acid  or  the  alkali — it  is  quite  neutral ;  it  is  called  in 
chemistry  a  salt,  and  the  name  of  this  particular  salt 
prepared  by  the  action  of  nitric  acid  on  soda  is  sodium 
nitrate  or  Chili  saltpetre. 

Salts. — There  are  many  different  salts.  Ordinary 
"  bluestone  "  is  a  salt  formed  by  the  action  of  sulphuric 
acid  on  copper  oxide ;  the  "  salt "  we  eat  is  a  salt  which 
may  be  formed  by  the  action  of  hydrochloric  acid  on 
soda,  but  most  of  that  which  is  used  in  commerce  is  not 
prepared  by  chemists,  but  is  obtained  from  the  earth. 

Bases. — You  see  we  have  formed  a  salt  by  the  union 
of  an  acid  with  an  alkali.  But  many  of  the  oxides  of 
the  metals  are  insoluble  in  water,  and  yet  when  dissolved 
by  acids  they  produce  salts.  Another  name  is  therefore 
given  to  all  the  substances  which  neutralize  acids ;  they 
are  called  Bases,  and  if  soluble  in  water  are  called 
ALKALIES. 


328  THE  FORCES  OF  NATURE. 

Let  us  see  what  we  have  learned  so  far.  First  we 
tried  to  understand  what  is  meant  by  an  element,  or 
simple  substance,  and  saw  that  the  elements  were  divided 
into  metals  and  non-metals :  then  went  on  to  consider 
the  oxides,  or  compounds  formed  by  the  different  ele- 
ments with  oxygen — the  oxides  of  the  non-metals  which, 
with  the  addition  of  water,  produce  acids,  and  the  oxides 
of  the  metals  which,  if  acted  upon  by  water  at  all,  give 
strong  alkaline  solutions,  but  are,  in  any  case,  called 
Bases  ;  and  finally  saw  that  the  Bases,  or  metallic  oxides, 
in  combination  with  acids,  produce  salts. 

Combustion. — We  had  occasion  earlier  in  this  book  to 
talk  of  substances  combining  with  oxygen,  and  I  want 
you  now  to  go  back  to  Chapter  XII.,  p.  210,  and  look 
again  at  what  was  said  there.  We  were  talking  of 
Forces  and  Energy,  and  found  (i)  that  one  of  the  forces 
which  can  give  rise  to  energetic  action  is  the  Chemical 
affinity,  or  tendency  to  combine  with  each  other,  that 
exists  in  different  substances,  and  (2)  that  until  it  is 
satisfied  by  bringing  about  the  desired  combination  it 
is  in  the  condition  of  potential  or  stored  up  energy, 
waiting  to  act ;  but  when  it  is  expended  or  paid  out  in 
doing  the  active  work  of  combining,  it  goes  off  into  some 
other  kind  of  energy,  heat,  light,  and  electricity  being 
the  most  usual  forms. 

Let  us  see  what  happens  when  a  fire  is  lighted.  The 
fuel  that  is  piled  in  the  grate  is  full  of  latent  or  hidden 
power,  for  it  is  always  waiting  for  a  chance  of  combining 
with  oxygen  ;  and  there  is  plenty  of  oxygen  in  the  air 
all  round,  only  while  the  fuel  is  cold  it  is  not  in  a 
favourable  condition  for  combination.  When,  however, 


COMBUSTION.  329 

we  bring  a  lighted  match  into  contact  with  the  paper, 
it  is  warmed  enough  to  rush  vigorously  into  combination 
with  the  oxygen,  and  the  energy  is  changed  into  so  much 
heat  that  the  faggot  is  heated  and  the  wood  begins  com- 
bining with  oxygen,  or  "burning."  This  combination 
again  sets  free  much  more  energy,  as  heat,  which,  in  its 
turn,  starts  the  combining  of  the  coals,  and  so  it  goes  on 
till  everything  combustible  within  reach,  that  is,  everything 
which  heat  can  readily  enable  to  combine  with  oxygen,  is 
combined  or  burnt  up.  The  paper,  wood,  and  coals  all 
contain  carbon,  and  the  new  substance  produced  by  the 
combination,  or  burning,  is  an  oxide  of  carbon,  com- 
monly called  carbonic  acid  gas,  which  we  will  presently 
examine. 

In  the  great  heat  caused  by  the  energetic  rush  of  com- 
bining, some  parts  of  the  solid  carbon  are  raised  to  such 
a  temperature  that  they  become  luminous,  or  give  out 
light.  The  glowing  red  hot  coal  is  a  luminous  solid, 
the  flame  that  dances  over  it  is  luminous  gas,  made 
more  brilliant  by  containing  tiny  solid  particles  of  white 
hot  carbon. 

Just  the  same  thing  happens  when  a  candle  burns.  It 
is  hot  because  the  wax  is  combining  energetically  with 
oxygen,  luminous  from  the  high  temperature  of  the  gas 
that  is  being  formed,  and  brilliant  from  the  white  hot 
particles  of  carbon  floating  in  the  gas. 

The  coal  and  the  candle  do  not  consist  of  carbon 
only ;  there  is  hydrogen  combined  with  the  carbon,  and 
the  hydrogen  being  set  free  in  the  burning  combines  also 
with  oxygen  and  forms  water  vapour.  If  we  hold  a  cold, 
bright  glass  tumbler  over  a  candle  flame,  it  immediately 


33O  THE  FORCES  OF  NATURE. 

becomes  misty  with  fine  steam,  because  the  cold  glass 
condenses  some  of  the  vapour  into  water.  All  the 
variety  of  paraffins  and  other  oils  that  we  burn  in  our 
lamps  are  also  combinations  of  hydrogen  and  carbon 
in  different  proportions ;  and  you  have  very  likely  noticed 
that  when  a  lamp  is  first  lighted,  and  the  cold  glass 
chimney  placed  over  the  flame,  it  turns  misty,  like  the 
tumbler,  with  the  steam,  but  in  a  minute  or  so  the  glass 
grows  too  hot  to  condense  the  water  and  so  becomes 
clear  again. 

None  of  the  matter  is  lost  or  destroyed  by  burning ; 
it  only  changes  its  combinations  and  exists  in  other 
forms ;  and  if  when  a  candle  is  burned  we  could  collect 
and  weigh  all  the  carbonic  acid  gas  and  water  vapour 
formed  by  its  burning,  we  should  find  that  their  weight 
was  exactly  that  of  the  candle  added  to  the  weight  of 
oxygen  with  which  it  had  combined. 

You  see  that  we  have  several  times  here  spoken  of 
"  combining  or  burning,"  and  I  want  you  to  notice  that 
"burning"  is  only  another  name  for  combining,  usually 
with  oxygen.  Some  substances  oxidize  with  a  swift 
violent  energy  which  produces  great  heat  and  light,  and 
some  oxidize  quietly  and  slowly,  though  more  or  less 
heat  is  almost  always  given  out  in  the  act  of  combining. 
In  common  talk  we  only  give  the  name  of  "  burning  "  to 
the  rapid,  hot,  bright  oxidizing;  but  chemists  will  tell 
you  that  all  oxidizing,  even  the  quietest,  is  really  "  burn- 
ing," or  combustion,  which  is  the  proper  word  for  it. 

Respiration. — Do  you  remember  when  we  first  had 
occasion  to  learn  the  name  of  carbonic  acid  gas  ?  How 
we  saw  that  in  breathing  we  draw  fresh,  clean  air  into 


RESPIRA  TION.  3  3 1 

our  lungs,  and  there  the  blood,  seizing  upon  the  oxygen 
in  the  air,  carries  it  along  in  its  ceaseless  travels 
(p.  151).  What  the  oxygen  does  in  the  blood  is  to 
combine  with  the  particles  of  waste  carbon  in  all  parts 
of  the  body,  forming  carbonic  acid  gas,  which  the  blood 
carries  back  to  the  lungs  to  be  breathed  out  and  so 
got  rid  of.  We  know  enough  now  to  call  the  process 
by  its  proper  name  of  combustion  or  burning,  and  can 
see  that  oxidizing  the  waste  carbon  is  simply  burning  it 
up,  just  as  the  carbon  in  the  coals  and  the  candle  are 
burnt,  and  the  heat  given  out  in  the  combination  is  what 
keeps  our  blood  warm  and  so  warms  our  bodies.  The 
heat  is  not  so  great  as  to  cause  flame  and  fire,  because 
the  combustion  which  is  always  going  on  is  spread  about 
all  through  the  blood,  and  not  concentrated  into  one 
spot.  So  all  the  warmth  of  living  animals  is  produced 
by  chemical  combination. 

The  effects  of  rapid  oxidation  are  sometimes  very 
sudden  and  startling  indeed.  Gunpowder  is  a  mixture 
of  sulphur,  charcoal  or  carbon,  and  nitre  or  potassium 
nitrate.  These  substances  are  powdered,  mixed  together 
carefully,  and  then  the  mixture,  after  having  been  wetted, 
is  squeezed  together  by  machinery  with  very  great 
pressure,  a  process  which  turns  the  moist  powder  into 
a  hard  slate-like  material  which  can  afterwards  be  broken 
up  into  pieces  of  any  desired  size.  When  gunpowder 
is  set  on  fire,  the  large  quantity  of  oxygen  in  the  nitre 
combines  with  the  carbon  and  sulphur,  and  forms  in  an 
instant  a  very  large  volume  of  gas  which,  expanding 
suddenly,  has  power  enough  to  hurl  aside  anything 
that  has  confined  it.  The  explosion  of  gunpowder  is, 


332  THE  FORCES   OF  NATURE. 

therefore,  nothing  more  than  the  very  quick  burning  of 
carbon  and  sulphur. 

Carbonic  Acid  Gas. — Now  let  us  examine  this 
carbonic  acid  gas,  which  chemists  call  carbon  dioxide. 

We  can  get  it,  as  we  know,  by  burning  carbon  in  the 
air,  but  another  and  a  convenient  way  of  preparing  it 
is  by  putting  some  pieces  of  chalk  or  marble  into  a 
wide-mouthed  jar,  such  as  a  pickle  bottle,  and  pouring 
gently  upon  them  some  hydrochloric  acid  and  water ;  the 
acid  must  be  carefully  handled,  as  it  is  poisonous.  There 
will  instantly  be  a  fizzing,  and  the  jar  will  soon  be  full 
of  the  gas,  with  a  little  liquid  at  the  bottom.  Marble 
and  chalk  are  different  forms  of  what  is  called  calcium 
carbonate,  a  compound  of  the  metal  calcium  with  carbon 
and  oxygen,  while  hydrochloric  acid  is  a  compound  of 
hydrogen  and  chlorine  dissolved  in  water.  When  they 
are  put  together  the  carbon  and  some  of  the  oxygen 
form  carbonic  acid  gas,  the  rest  of  the  oxygen  and  the 
hydrogen  become  water,  and  the  calcium  and  chlorine 
combine  into  calcium  chloride,  which  is  left  dissolved  in 
the  water  at  the  bottom  of  the  jar. 

If  we  test  the  carbonic  acid  gas  as  we  did  the  oxygen 
and  the  hydrogen,  we  shall  find  that  it  has  neither  colour 
nor  smell,  that  it  will  neither  burn  nor  allow  anything 
else  to  burn  in  it.  Nor  indeed  can  anything  live  in  it ; 
a  living  creature  that  gets  into  it  will  soon  die. 

When  we  wanted  to  keep  hydrogen  in  a  jar,  we  found 
it  necessary  to  turn  the  jar  upside  down,  because  the 
light  hydrogen  would  all  rise  into  the  air  and  fly  away, 
but  this  gas  does  not  show  any  sign  of  doing  so. 

Put  a  second  jar,  empty  and  clean,  beside  the  one 


CARBONIC  ACID    GAS. 


333 


we  are  using,  light  a  match  or  a  taper,  and  dip  it  first 
into  the  empty  jar,  where  it  burns  easily,  and  then  into 
the  gas,  where  it  instantly  goes  out.  Now  take  the  jar 
of  gas  and,  holding  it  over  the  mouth  of  the  empty  jar, 
pour  carefully  from  one  to  the  other;  but  take  care  not 
to  let  any  of  the  liquid  at  the  bottom  pass  out.  If, 
after  this,  you  test  again  with  the  lighted  match,  you 
will  find  that  it  is  now  extinguished  in  the  second  jar — 
showing  it  contains  carbonic  acid  gas ;  the  gas  has  been 
literally  poured  from  one  jar  to  the  other,  proving  that 
it  is  a  very  heavy  gas. 

We  have  produced  some  carbonic  acid  gas  from  chalk ; 
now  let  us  go  the  opposite  way  to  work,  and  see  if  we 
can  get  chalk  again  by  means  of  the  gas.  For  this 
purpose  we  will  put  some  pieces  of  ordinary  quick-lime, 
which  is  an  oxide  of  calcium,  into  a  large  bottle,  nearly 
fill  it  up  with  water,  shake,  and  then  allow  it  to  stand 
for  two  or  three  days ;  after  which  time  the  solid  lime 
will  have  sunk  to  the  bottom,  leaving  above  a  clear 
liquid,  which  is  lime  water — that  is,  water  with  some  of 
the  lime  dissolved  in  it.  We  can  pour  off  the  lime  water 
into  an  empty  jar,  leaving  the  sediment  behind.  If  this 
is  done  steadily  and  without  shaking,  the  lime  water 
remains  quite  clear.  Now,  however,  let  us  pour  a  little 
of  it  into  a  jar  containing  carbonic  acid  gas,  and  we 
find  that  the  lime  water  instantly  turns  milky.  The 
reason  of  this  is  that  the  carbonic  acid  combines  with 
the  lime  in  the  water  and  forms  chalk  (calcium  car- 
bonate). Chalk  will  not  dissolve  in  water  like  lime, 
and  the  tiny  particles  of  solid  chalk  suspended  in  the 
water  cause  the  milky  appearance. 


334  THE  FORCES  OF  NATURE. 

We  can  make  the  lime  water  look  milky  just  as  well 
by  simply  blowing  into  it  some  of  the  carbonic  acid  gas 
from  our  lungs.  Let  us  take  some  of  the  clear  lime 
water  in  a  test-tube,  and  blow  gently  into  it  through  a 
piece  of  glass  tube  until  it  becomes  milky ;  do  not  stop 
then,  however,  but  continue  blowing,  and  in  a  few 
minutes  all  themilkiness  disappears  and  the  liquid  is 
clear  again.  What  is  the  reason  of  this?  It  is  that 
chalk,  though  it  will  not  dissolve  in  pure  water,  does 
dissolve  in  a  solution  of  carbonic  acid.  Our  first  breaths 
of  carbonic  acid  only  converted  the  lime  into  chalk ; 
but  when  this  change  was  complete  the  chalk  would  not 
take  up  any  more  of  the  carbonic  acid,  which  went  on 
passing  into  the  water,  and  soon  brought  it  to  a  condition 
in  which  it  could  dissolve  the  chalk.  Our  clear  water 
now  is,  therefore,  not  the  same  as  the  clear  water  we 
began  with.  That  contained  dissolved  lime,  but  this 
contains  chalk  dissolved  in  carbonic  acid. 

If  we  now  suspend  the  test-tube  over  a  spirit  lamp 
and  make  the  water  boil,  the  excess  of  carbonic  acid 
gas  is  driven  off  in  the  boiling,  and  the  chalk,  no  longer 
having  anything  which  can  dissolve  it,  reappears  in 
milkiness. 

Hard  and  Soft  Waters. — We  will  test  our  clear 
waters  in  yet  another  way.  Here  is  a  tub  that  has  been 
left  out  in  the  garden,  and  is  half  full  of  rain  water.  If 
we  put  some  into  a  basin  and  wash  our  hands  in  it  they 
are  quickly  clean,  for  the  soap  lathers  up  directly ;  indeed, 
if  we  use  a  good  deal  and  beat  up  the  water  for  a  minute 
it  becomes  a  mass  of  soap  bubbles. 

Now  try  washing  in  the  water  which  contains  dissolved 


DIFFUSION  OF  GASES.  335 

chalk,  and  we  shall  find  the  difference ;  at  first  we  can- 
not get  a  lather  at  all,  but  presently  there  will  come 
little  flakes  like  curd,  and  after  a  little  perseverance  the 
soap  will  lather.  This  is  what  we  call  a  hard  water, 
while  the  rain  gives  us  a  soft  water.  Pure  water  is 
always  soft.  But  if  our  water  is  hard  through  the  pre- 
sence of  chalk  dissolved  in  carbonic  acid,  we  know  now 
how  to  soften  it.  By  boiling  the  water  (as  we  saw  just 
now  in  the  test-tube),  the  excess  of  carbonic  acid  is 
driven  off,  and  the  chalk,  no  longer  dissolved,  falls  down 
as  a  white  mud,  forming  a  white  coating,  or  furr,  on 
the  inside  of  the  kettle  or  boiler,  but  leaving  the  water 
fairly  pure  and  therefore  soft. 

This  kind  of  hardness  which  may  be  removed  by 
boiling  is  called  temporary  hardness.  But  if  instead  of 
chalk  the  water  contains  dissolved  gypsum  (sulphate  of 
lime),  or  common  salt,  like  sea  water,  this  cannot  be 
removed  by  boiling,  but  gives  rise  to  what  we  call  per- 
manent hardness. 

Diffusion  of  Gases. — Since  all  burning  forms  car- 
bonic acid,  and  all  animals  breathe  out  this  poisonous  gas, 
you  may  perhaps  wonder  where  it  all  goes  to,  and  why, 
as  it  is  so  heavy,  it  does  not  all  lie  about  on  the  surface 
of  the  earth,  and  kill  all  animals,  and  put  out  all  fires. 

Well,  there  are  two  reasons  why  this  is  not  the  case. 
First,  it  is  not  possible  to  keep  a  gas  by  itself  at  all, 
unless  it  is  tightly  shut  up  in  some  vessel ;  if  any  other 
gas  can  reach  it,  no  matter  how  much  difference  in 
weight  there  is  between  them,  they  will  gradually  mix 
together.  Heavy  gases  will  go  upwards,  if  necessary, 
and  light  ones  will  come  down,  each  diffusing  itself 


336  THE  FORCES  OF  NATURE. 

through  as  large  a  space  as  possible.  It  is  true  that 
we  were  able  to  pour  carbonic  acid  gas  from  one  vessel 
to  another,  and  also  that  when  hydrogen  was  produced 
by  the  action  of  sulphuric  acid  on  zinc,  we  caught  some 
of  it  in  a  jar  turned  upside  down.  But  in  both  these 
cases,  we  have  to  experiment  quickly  with  the  gases 
before  they  are  lost  by  diffusion  in  the  air,  which  will 
soon  occur  unless  they  are  kept  bottled  up.  So  we  see 
that  even  the  heavy  carbonic  acid  gas,  if  only  it  has 
free  access  to  the  air,  gradually  diffuses  itself  into  the 
whole  atmosphere.  Where,  however,  it  is  confined  with 
little  opportunity  of  mixing  with  air,  it  becomes  a  real 
danger.  In  coal  mines  it  forms  the  terrible  choke-damp  ^ 
and  it  frequently  occurs  at  the  bottom  of  old  wells; 
even  rooms  where  several  persons  have  been  breathing 
become  unwholesome  with  carbonic  acid,  unless  pure  air 
is  freely  admitted  so  as  to  mix  with  it.  Winds  and 
convection  currents  (p.  253)  are  energetic  helpers  in  this 
mingling  of  the  gases  of  the  atmosphere. 

But  there  is  a  second  and  very  important  process 
going  on,  by  which  carbonic  acid  is  not  merely  dissipated 
but  actually  destroyed.  This  is  the  action  of  plants, 
which  when  exposed  to  sunlight  absorb  carbonic  acid 
from  the  air,  and  separating  the  oxygen  and  carbon, 
send  back  the  oxygen  into  the  air  while  they  feed 
themselves  upon  the  carbon  (see  p.  195).  Thus  we 
find  that  while  men  and  other  animals  absorb  oxygen 
and  breathe  out  carbonic  acid,  plants  and  trees  absorb 
the  carbonic  acid  and  give  out  oxygen,  so  purifying 
the  air  and  making  it  fit  to  be  breathed  again  by  men. 

Summary. — You  will  observe  that  almost  the  whole 


CONCLUSION.  337 

of  what  we  have  learnt  in  this  chapter  is  about  Oxygen 
and  its  combinations — how  with  metals  it  forms  bases, 
and  with  non-metals  acids,  and  how  bases  and  acids 
combine  into  salts  ;  how  the  process  of  combining  with 
oxygen  is  the  same  thing  as  combiistion  ;  and  finally,  we 
considered  the  slow  form  of  combustion  called  respira- 
tion or  breathing,  and  the  carbonic  acid  gas  which  is 
produced  by  respiration. 

But,  as  there  is  not  time  or  space  to  go  further  into 
Chemistry  here,  the  whole  subject  of  combinations 
between  the  other  elements,  as  well  as  the  question  of 
the  fixed  numerical  proportions  in  which  elements  com- 
bine, and  many  other  important  laws  of  chemistry,  must 
all  be  left  for  future  study. 

In  the  last  ten  chapters  we  have  made  a  beginning  of 
the  study  of  the  vast  and  various  forms  of  Energy  among 
which  we  live  and  move.  And  we  see  that,  though  we 
are  not  able  to  create  or  destroy  these  natural  Forces, 
yet  we  learn  by  experience  first  to  adapt  ourselves  so 
as  to  live  at  peace  with  them,  and  then  by  degrees  to 
guide  and  transform  and  use  them  for  our  own  purposes. 
Yet  men's  knowledge  is  still  very  limited,  and  it  is  open 
to  every  thoughtful  and  accurate  observer  of  nature  to 
do  something  to  increase  the  sum  of  human  knowledge 
and  power. 


INDEX 


A 

Aphis,  126 

Apple  blossom,  parts  of, 

179 

Acids,  325-328 

Arachnida,  124,  128 

Adder,  112 
Affinity,  chemical,  204,  303 

Arctic  dogs,  44 
Arm,  bones  of,  141,  144 

Agoutis,  So                                           Armadillo,  84 

Air,  composition  of,  318                !   Arteries,  mo 

Air-pump,  281 

Arthropoda,  15,  17,  123-129,  154 

Albatross,  102                                     Asparagus,  174 
Alimentary  canal,  157                       Ass-  ^  „ 

Alkalies,  326,  327 
Alligators,  109 

Assapan,  75 
Auricles,  150 

Allotropy,  321 

Aurochs,  6  1 

Alpine  marmot,  75 

Axolotl,  114 

Aluminium,  317 

Amblystoma,  114 

American  monkeys,  32 

B 

Amreba,  17,  136 

Amphibians,  10,  112-114,  15* 

Baboon,  31 

Analysis  of  water,  309 

Backbone,     the    jointed, 

138- 

Anchovy,  119 

(See  also  Vertebrata) 

Animal  kingdom,  table  of,  20 

Badger,  48 

Ant-eaters,  82,  90 

Ball  armadillo,  84 

Antelopes,  63 

Barbary  ape,  30 

Antlers  of  deer,  etc.,  66 

Barbel,  119 

Ants,  125 

Barbels,  98 

Ant  thrush,  100 

Barnacles,  129 

Apes,  25-33                                       Barometer,  229 

,  distinctions  of,  25                    Bases,  327 

,  likeness  to  man,  26                 Bats,  33,  142 

340 


INDEX. 


Battery,  electric,  304 

Bushboks,  64 

Bean,  181,  183 

Buttercup,  167,  172 

Bears,  46 

,  parts  of,  179 

Beasts  of  prey,  37-49,  142 

Butterflies,  125,  126 

Beaver,  75 

Bees,  125 

Beetles,  125 

C 

,  large  number  of  species, 

121 

Cabbage,  leaves  of,  1  74 

Bell-bird,  100 

Calcium,  317,  332 

Big  horn  sheep,  63 

Camel,  70 

Bile,  156 

Cape  ant-eater,  83 

Bindweed,  170 
Birds,  9,  91-106,  139,  143,  147, 

Cape  hunting-dog,  44 
Capillary  tubes,  150 

154 

Capybara,  80 

,  characteristics  of,  91 

Carbon,  321,  329-337 

,  eggs,  92 

Carbonic  acid  gas,  330-337 

nests,  105,  106 

Carnivora,  37-49 

of  Paradise,  99 

Carp,  119 

of  prey,  94 

Carrots,  174,  177 

Bison,  6  1 

Cat  family,  38-42 

Bivalve  shells,  123 

Caterpillar,  15 

Blackbird,  99 

Catkins,  176 

Blood,  150-155 

Cavy,  80 

corpuscles,  153,  154 

Cells,  organic,  17,  136 

Boars,  57 

,  voltaic  or  galvanic,  303 

Body,  the  human,  137-164 

Centigrade  thermometer,  244 

Boiling  point,  243,  250 

Centipede,  15,  127 

Box  tortoise,  108 

Cetacea,  50,  119 

Brain,  the,  157,  160 

Chameleon,  in 

Branches  of  plants,  170-175 

Chamois,  65 

Breastbone,  140 

Chemical  affinity  or  attraction, 

Breathing,  330 

204,  303 

Brill,  118 

Chevrotains,  69 

Bromine,  323 

Chewing  the  cud,  59,  72 

Broom,   181 

Chimpanzee,  29 

Bryony,  170,  173 

Chinchillas,  80 

Buffalo,  6  1 

Chinese  water-deer,  67 

Butterfly,  15 

Chiroptera,  33 

Bugs,  127 

Chlorine,  317 

Bull-finch's  nest,  106 

Cicads,  127 

Burrowing  owl,  75 

Civets,  42 

INDEX. 


341 


Classification  of  animals,  3  -24 

Clavicle,  140,  142 

Climbing  birds,  97 

Cloven  foot,  the,  59-72 

Cobra,  112 

Cockroaches,  127 

Cod,  118 

Coelenterata,  16,  18,  132 

Cohesion,  force  of,  202,  234 

Collar-bone,  140,  142 

Colour,  263 

Colugo,  37 

Combustion,  328 

Compass  needle,  290,  302 

Compounds,  313 

Condor,  95 

Conduction  of  heat,  254 

of  electricity,  293 

Conductors,  good  and  bad,  256 

Coney  family,  53 

Coniferae,  189 

Convection,  252 

Convolvulus,  170,  173 

Copper,  317 

Coral,  133 

Cotyledons,  184 

Cows,  60 

Crabs,  129 

Crakes,  101 

Craneflies,  127 

Crickets,  127 

Crocodiles,  109,  154 

Crocus,  169 

Crows,  99 

Crustaceans,  125,  129 

Crystallization,  237 

Cuckoo,  1 06 

Cuckoo  flower,  176 

Current  electricity,  302 

Cuscus,  87 

Cuttle-fish,  1 22 

Cynocephalus,  31 


Daffodil,  175 
Daisy,  169,  175 

,  parts  of,  177-179,  1 86 

Dandelion,  169 
Decomposition,  chemical,  311 
Deer,  66,  142 
Density,  218 

of  water,  250 

Diaphragm,  the,  147,  155 

Dicotyledons,  185 

Diffusion  of  gases,  335 

Dingo,  44 

Dog  family,  43-46 

Dolphin,  51 

Donkey,  55 

Dormouse,  78 

Dragon-flies,  127 

Duck,  102 

Duckbilled  Platypus,  89 


E 

Eagles,  95,  106 
Ear,  the,  161,  162 
Earthworm,  129,  165 
Earwigs,  127 
Echidna,  90 

Echinoderma,  16,  18,  131 
Edentata,  80-85 
Eels,  119 
Efts,  114 

Egg,    character     and    develop- 
ment of,  93 

Egg-laying  mammals,  89 
Eland,  64 
Electricity,  205,  292-308,  311 

,  current  or  voltaic,  302 

,  doubleness  of,  294 

,  frictional,  292 


342 


INDEX, 


Electric  distribution,  298 

Flying  lemur,  36 

induction,  300 

squirrel,  74 

telegraph,  305,  306 

Focus  of  rays,  274 

telephone,  277 

Food,  analysis  of,  156 

Electrolysis,  307 

Foraminifera,  135 

Electro-magnet,  304 

Force,  definition  of,  205 

Electroscope,  296 

Forces  of  nature,  199,  et  seq. 

Elements,  313,  316 

Fox,  44 

Elephant,  52,  142 

Freezing-point,  243,  250 

Elk,  68 

Friction,  205 

Energy,  definition  of,  207 

Frictional  electricity,  292 

,  potential  and  kinetic,  208 

Froghopper,  127 

,  transformation  of,  211 

Frogs,  10,  113,  154,  164 

Entellus  monkey,  31 

Fusion,  248 

Ether,  257 

Evaporation,  236 

Expansion,  241,  251 

Eye,  the,  162-164 

Galvanic  cell,  303. 

Galvanometer,  306 

F 

Game  birds,  ico 

Gases,  diffusion  of,  335 

Fahrenheit  thermometer,  244 

—  ,  pressure  of,  225 

Falcon,  94,  96 

Gastric  juice,  156 

Fallow  deer,  68 

Gazelle,  64 

Ferret,  48 

Gecko,  in 

Finches,  100 

Geese,  102 

Fishes,    10,    n,    115-120,   140, 

Gemsboks,  64 

144,  154 

Genealogical  Tree,  23 

,  breathing  of,  9,  1  1  5 

Gibbon  ape,  29 

,  characteristics  of,  115 

Giraffe,  65,  139 

Fishing  eagle,  95 

Gnats,  127 

Flamingo,  101 

Gnu,  64 

Flat  fishes,  118 

Goat,  63 

Fleas,  126 

suckers,  98 

Flies,  126,  127 

Gold,  317,  324 

Flounder,  118 

Gorilla,  26,  143 

Flowerless  plants,  189 

Grand  eland,  64 

Flowers,  175 

Grass,  175 

,  irregular,  181 

Grasshopper,  127,  147 

,  parts  of,  177-182 

Gravitation,  force  of,  199-202 

Fluids,  pressure  of,  223 

Great  ant-bear,  82 

Flying  fox,  34 

Greenfly,  127 

INDEX. 


343 


Grizzly  bear,  47 

Ground  squirrel,  75 

Grouse,  100 

Gulls,  102 

Gunpowder,  constituents  of,  331 


H 

Hare,  80 
Hartebeests,  64 
Harvest  mouse,  78 
Hawks,  95 
Heart,  the,  148 
Heat,  203,  235,  241-257 
Hedgehog,  35 
Hemlock,  flower  of,  177 
Herons,  lor 
Herring,  118 
Hippopotamus,  58 
Hog,  57 
Hollyhock,  172 
Honey  guides,  98 
Honeysuckle,  175 
Hoofed  animals,  52-73 
— ,  divisions  of,  54 
Hornbills,  98 
Horns,  66 
Horse,  54,  142 
Howler  monkeys,  32 
Humerus,  140 
Humming  birds,  98,  106 
Hyacinth,  175 

Hydrogen,  312,  317,  326,  329 
Hyena,  42 
Hyracoidea,  53 


Ice,  231,  250 

Illustrations,  list  of,  xv.-xviii. 
Induction,    electric    and    mag- 
netic, 300 


Insect    eaters,   or    Insectivora, 

34-37,  142 
|    Insects,  123,  125 

,  nerve  system  of,  165 

i   Insulator  electrical,  294 

Invertebrata,  8,  12-18,  121-136, 
154 

,  nerve  system  of  the,  165 

Iodine,  323 

Irish  elk,  69 

Iron,  317 

Italian  shrew,  35 

J 

Jackal,  45 
Jays,  99 
Jelly-fish,  133 
Jumping  mouse,  or  jerboa,  78 


Kalong,  or  flying  fox,  34 
Kangaroo,  85,  142 
—  hare,  87 

rats,  87 

Kidneys,  the,  153 
Kinetic  energy,  208 
Kingfishers,  98,  106 
Kite,  95 

Koala,  or  Australian  bear-,  87 
Koodoos,  64 


TT 


Laburnum,  181 
Lampreys,  12 
Lancelot,  12 
Land  carnivora,  37-48 

,  distinctions  of,  37 

Land  crabs,  129 
Lark,  100 


344 


INDEX. 


Larva,  125 

Manatee,  51,  141 

Latent  heat,  248 

Marine  cornivora,  48,  49 

Lead,  317 

Mariner's  compass,  290 

Leaves,  174,  175 

Marmot,  75 

Legs,  bones  of,  141 

Marsupials,  85-89 

LeguminosDS,  186 

Marten,  48 

Lemurs,  32 

Mayflies,  127 

Lenses,  273,  274 

Mercury,  230,  243,  317 

Leopard,  or  panther,  42 

Metals,  316 

Light,  258-275 

Mice,  77 

,  electric,  307 

Midges,  127 

,     reflected,      transmitted, 

Millipedes,  128 

absorbed,  261 

Mole,  35 

Lilies,  175 

Mollusks,   or  mollusca,   16,  17, 

Lily  of  the  valley,  169,  180 

122,   154 

Lion,  40,  143 

Momentum,  217 

Lithium,  317 

Monitor  lizard,  1  10 

Litmus,  325 

Monkeys,  30-33 

Liver,  the,  156 

Monocotyledons,  187-189 

Livingstone,  Dr.,  41 

Monotremata,  89 

Lizard,  no,  140 

Moorhens,  101 

Llamas,  71 

Moose,  68 

Lobsters,  129 

Mosquitoes,  127 

Luminiferous  ether,  257 

Moths,  125,  126 

Luminous  bodies,  259 

Motion  and  sound,  278 

Lungs,  the,  152 

Motor  nerves,  159,  160 

Lyre  bird,  100 

Moufflon,  63 

Mouse,  77 

Mullein,  172 

M 

Muscle,  145-147 

Mackerel,  118 

Music,  282-284 

Magnesia,  324 
Magnetic  field,  288 
curves,  288,  289 

Musk  deer,  67 
Musk  ox,  62 
Myriopoda,  124 

needle,  290 

Magnetism,  285-291 

M 

of  the  earth,  291 

Magpies,  99 

Native  devil  of  Tasmania,  88 

Mammals,  or  mammalia,  9,  33— 

Nervous  system,  the,  157-166 

90,  140,  153 

Nests,  105 

Man,  25 

Newts,  114 

,  body  of,  137-164 

Nightingale,  99 

INDEX. 


345 


Nitrogen,  318                                  |   Picarian  birds,  96 

Non-metallic      elements,     316,       Pigeons,  100 

317,321                                       i   Pigs,  57 

Pimpernel,  175 

Pipe  fish,  i  i  7 

O 

Plaice,  118 

Oak,  168,  172 

Plantain,  169,  175 

Octopus,  122 
Onions,  leaves  of,  174 
Opacity,  260 
Opossum,  88 
Orang-outang,  29 
Osprey,  95 
Ostrich,  103,  106 
Otter,  48 
Owls,  75,  94,  96 
Oxen,  60 

Plantain  eaters,  98 
Plants,  167-198 
—  ,  parts  of,  175-181 
,  flowerless,  189 
,  life,  192-198 
—  ,  tissues  of,  193 
,  food  of,  194-198 
,  use  of,  336 
Platinum,  317,  324 
Platypus,  89 

Oxidation  and  oxides,  323-328, 

Plovers,  101 
Pod-bearing  plants,  186 

331 
Oxygen,    313,    317,    318,     323, 

Polar  bear,  47 
Polarization,  304 

324 

Polecat,  48 

Oysters,  123 

Poles,  the  magnetic,  287 

Polypes,  134 

p 

Poppy.  175 

Porcupine,  79 

Pancreatic  juice,  156 

Porpoise,  51 

Pangolin,  83 

Potassium,  317 

Panther  or  leopard,  42 

Potato,  169 

Parrots,  97 

Potential  energy,  208 

Parsley,  flowers  of,  177                  '   Potoroos,  87 

Partridges,  IOO                                    Pouched  animals,  85-89 

Pea,  tendrils  of,  173,  174 

Prairie  "  dog,"  75 

Peacocks,  too 

Prawns,  129 

Peccaries,  58 

Pressure  of  fluids,  223 

Pelvis,  the,   141 

gases,  225 

Penguins,  102 

Primrose,  1  80,  1  86 

Perch,  119 

Prism,  273 

Perching  birds,  98 

Proboscidea,  52 

Phalangers,  87 

Protoplasm,  193 

Pheasants,  100 

Protozoa,  17,  18,  135 

Phosphorus,  318,  322,  325 

Puma,  42 

346 


INDEX. 


Pump,  working  of  a,  226 
Pupa  stage  of  insects,  125 


Quadrumana,  25 
Quagga,  55 

Quicksilver,    or    mercury,    230, 
243,  31? 


Rabbits,  80 

Radiation,  256 

Radius  of  arm,  141,  144 

Rails,  10 1 

Rats,  77 

Reflexion,  261,  264-273 

Refraction,  267-275 

Reindeer,  69 

Reptiles,  10,  107-112,  140,  154 

Resistance,  sense  of,  205 

Respiration,  330 

Rhinoceros,  56 

Rodents,  73-80,  142 

,  distinction  of,  73 

Rooks,  99 
Roots,  167-170 
Rose  tree,  1 70,  1 74 
Ruminants,  59 

,  horns,  59 

,  teeth  of,  70 


Salamanders,  114 
Saliva,  155 
Salmon,  116,  120 
Salts,  327 

Sand-martin's  nest,  106 
Scallops,  123 


Scaly  ant-eater  or  pangolin,  83 

Scarlet  runners,  leaves  of,  174 

Scorpions,  128 

Sea  anemone,  15,  16,  133 

Sea  cucumbers,  132 

Sea  lilies,  132 

Sea  lions,  48 

Seals,  48,  49 

Sea-squirts,  12 

Sea  urchins  or  sea  eggs,  132 

Sea  worms,  130 

Seed,  development  of,  183-185 

Senses,  special  organs  of,  161 

Sensory  nerves,  159,  160 

Serpula,  130,  147 

Shark,  117 

Sheep,  62 

Shells,  122,  123 

Shrew,  35 

Shrimp,  15,  129 

Silicon,  317 

Silver,  317,  324 
I    Sirenia,  51 

Skates,  ilS 

Skeletons,  similarities  in,  143 

Skin,  the,  152 

Skull,  the,  138 

Sky-lark,  100 

Sloth,  81,  139,  142 

Slug,  15 

Snail,  15 

Snake,  III,  140,  141,  143 
— ,  skeleton  of,  5,  143 
,  fangs  of,  112 

Sodium,  317,  324,  326 

Sole,  118 

Solens,  123 

Solution,  236 
Song  birds,  99 
Sound,  276-284 

Connection  with  motion,  278 

Space,  207 


INDEX. 


347 


Sparrow,  106                                     Termites,  127 

Specific  gravity,  219-222                  Thermometer,  the,  242,  249 

heat,  246                                   Thrush,  99,  106 

Spider  monkeys,  32 

Thylacinus,  88 

Spiders,  128,  166 

Tiger,  41,  147 

Spine,  the,  137 

Tissues  of  plants,  193 

Spiny  ant-eaters,  90 

Titmouse,  100,  106 

Sponge,  16,  134 

Toads,  113 

Sprats,  119 

Toothless  animals,  or  Edentata, 

Springboks,  64                                      80-85 

Springtails,  127                                   Tortoise,  107,  140 

Spruce  fir,  170                                     Toucans,  98 

Squirrel  monkeys,  32                          Translucency,  260 

Squirrels,  73 

Transparency,  260 

Starfish,  15,  131,  165 

Trogons,  98 

Starling,  100 

Trout,  119 

Steinboks,  64                                       Tunicata,  12 

Stems  of  plants,  170-175                   Turbot,  118 

Sternum,  the,  140                               Turnip,  169 

Sticklebacks,  1  16                                Turtles,  108 

Stoat,  47 

Stomach,  the,  155 

Storks,  101,  1  06 

U 

Strawberries,  leaves  of,  174 

Ulna,  the,  141 

Ungulata,  54~73 
Sunfish'M7                                       Univalve  shells,  122 
Swallow,  100,  106,  147                     Ursine  dasyure)  8? 

Swan,  102 

Sweet-pea,  181 

Swine,  54,  57 

V 

Sword  fish,  117 

Vacuum,  281 

T 

Veins,  151 

Velocity  of  falling  objects,  215 

Tadpole,  113 

light,  275 

Tailor  bird,  106 

sound,  276 

Tamandua,  82 

Ventricles,  150 

Tapir,  55 

Vertebrae,  the,  138,  139 

Telegraph,  electric,  305 

Vertebral  column,  the,  137 

Telephone,  277 

Vertebrata,  8-12 

Temperature,  244 

—  ,  nerve  system  of  the,  164 

Tench,  119 

Vibration,  279,  280 

348 


INDEX. 


Viper,  112 

Virginia  creeper,  170,  174 

Voltaic  electricity,  302 

cells,  303 

Vultures,  95 


W 

Waders,  101 
Wagtails,  100,  106 
Wallflower,  186 
Walrus,  48,  49 
Warblers,  99 
Wasp,  15,  125 
Water,  231 

,  analysis  of,  309 

birds,  102 

—  deer,  Chinese,  67 

,  density  of,  250 

fleas,  129 

,  hard  and  soft,  334 

pig,  80 

wagtail's  nest,  1 06 

Weasels,  47 
Weight,  214 
Whales,  50,  141,  147 


White  ants,  127 

light,  262,  263 

Wild  ass,  55 

boar,  57 

dogs,  44 

sheep,  63 

Wildebeest,  64 
Wingless  birds,  103 
Wolf,  45 
Wombat,  87 
Woodlice,  129 
Woodpecker,  96 
Wool,  72 

Work,  definition  of,  207 
Worm,  14,  16,  17,  129 
Wrens,  loo,  106 


Yak,  6 1 


Zebra,  55 

wolf,  88 

Zoophytes,  16,  134 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 

Los  Angeles 
This  book  is  DUE  on  the  last  date  stamped  below. 


NOV  2 


Form  L9-25m-9,'47(A5618)444 


Q 


AA    000478602 


Q 

163 

A96e 


